US Robotics COURIER HST User'smanual

[]11ilobotic:;

-------

HST™-

MODEM

-

9600

/

2400

/

1200

/

300

BPS, AUTO DIAL, AUTO ANSWER

MODEM

M610

-0 1

01

-00

WITH USR

HSr

M ERROR CONTROL

USER'S

MANUAL

USRobotics, Inc.

8100 North McCormick Blvd.
Skokie.

IL

60076

c

1986.

All

Rights

Re

se

rved

Courier

HST

is

a trademark

of

USRobotics. Inc.

Touch-Tone

and

Di

gital Data Service

(DDS)

are trademarks

of

American Telephone and Telegraph . MCI Mail is a service

mark

of

MCI

Communications.

Incorporated. Microcom Networkin g Protocol

(MNP)

is

a trademark

of

-"'1icrocom. Inc. Sprint

is

a trademark

of

General Telephone and

Electric.

Limited

Warranty

FCC

Registration

Connecting

to the

Telephone

Company

Radio

and

Television

Interference

For

Canadian

Modem

Users

How

to Use this Manual

COURIER HST

TABLE

OF CONTENTS

Vil

Vlll

VIII

IX

X

XI

PART

I.

INSTALLATION

AND

OPERATION

CHAPTER

I-Introduction

USR-HST

Trellis

Coded

Modulation

Asymmetric

Modulation

Enhanced

Error Control

Shorter

Response

Time

The

Courier

Product

Family

Courier

HST

Compatibility

CHAPTER

2-Set-Up

and

Testing

Package

Components

Operational

Requirements

Assembling

the

Modem

Testing

Analog

Loopback Self-Test

Additional Test Procedures

CHAPTER

3-0perations

at a

Glance

Data

Format

Error

Control

Dialing

HST-Compatible,

9600

bps

MNP-Compatible,

2400

or

1200 bps

Non-MNP

Compatible,

2400,

1200,

300

bps
Flow Control
Maximum

Throughput

High-Speed

Channel

Turnaround
Link Negotiation
Data

Rate Defaults

Nonvolatile

Memory

(NRAM)

Phone

Number

Storage

Dialing Stored

Numbers

1-1

1-1
1-1

1-1

1-1
1-1

1-3
2-1
2-1

2-1
2-2
2-5

2-6
2-7

3-1
3-1

3-1
3-1
3-1
3-1
3-2
3-2
3-2
3-2
3-2
3-3
3-3
3-3
3-3

iii

COURIER HST

IV

Busy Answer
Inactivity

Timer

CHAPTER

4-Interface

Controls

Terminology
Error Control

ARQ

Retry

Timer
Error Control Modes (&Mn)
With Auto Answer

Flow Control

Commands
Transmit Data Flow Control (&Hn)
Received Data Flow Control

Software Control (&In)
Hardware Control (&Rn)

Data Rate

Commands
Optional Fixed Rates
Terminal Rate Select (&Bn)
Link Rate Select (&Nn)
Rate-Select Guidelines

DSR Override (&Sn)

CHAPTER

5-Internal

Controls

Setting/Using Defaults

Writing Defaults to

NRAM

(&W)
Loading the Factory Defaults (&F)
Resetting to

NRAM

Defaults (Z)

Storing Telephone Numbers

(&Zn=

s)

Result Codes

Response Modes (Vn)
Result Code Sets

(Xn)

Result Codes Options Table

Options

Summary
Quiet Mode (Qn)
/ARQ

Result Codes (&An)

Local Echo

Command

Mode Local Echo (En)

Online Local Echo (Fn)

The Audio Monitor

Speaker Control (Mn)

Modem

Clock Usage (Kn)

Transmitter Enable/Disable (Cn)

Break Handling (&Yn)

The S-Registers

3-4
3-4

4-1
4-1

4-1
4-1
4-2
4-2
4-2
4-3

4-4

4-4

4-5
4-5
4-5

4-6
4-6
4-6

4-7

5-1
5-1

5-1

5-2
5-2
5-2
5-3
5-3
5-3

5-4

5-4

5-5

5-5
5-5

5-5

5-6
5-6
5-6

5-7
5-7

5-8
5-8

CHAPTER

6---Dialing and Answering

Basic Requirements

Transmission Rate

Error Control
Automatic Retrain

Placing Calls

Dial (D)

Dialing Type (T.

P)
Adaptive Dialing
Pause ( ,)
Dial and Return to

Command

Mode (;)

Dialing Letters

(")
Transferring Calls ( ')
Wait for a Second Dial Tone (W)
Wait for an Answer

((

i

t)

Reversing Originate/ Answer Frequencies

Canceling Dialing

Redialing

Reexecute the Last

Command

(A/)

Automated Redialing

Continuous Repeat ( > )
Continuous Reexecute (A> )
Exiting Repeat Mode

Dialing a Stored Number (DSn)
Pulse Dial Make/Break Ratio (&Pn)
Escape Code Operations (

+ + + )

ARQ

Mode Response

Normal Mode Responses

Returning Online

(0)
Hanging UP (Hn)
Automatic Answering

Suppressing Auto Answer
Points to Remember

U.S./CCITT

Answer Tone (Bn)

CHAPTER

7-Queries

and Help Screens

User

Inquiries (In)

S-Register Query (Sr?)

Sl7

S20

COURIER HST

6-1
6-1

6-1
6-1
6-2
6-2
6-2
6-2
6-3
6-3

6-4

6-5
6-5
6-5
6-6
6-6
6-6
6-7
6-7
6-7
6-7
6-7
6-7
6-8
6-8
6-8
6-9
6-9
6-9

6-10
6-10

6-10

6-10
6-11

7-1
7-1

7-3
7-3
7-3

V

COURIER HST

vi

Phone Number Query

(&Z11

'

1)

Help Screens

Basic Command Set

($)

Extended Command Set

(&$)

S-Rcgister Functions (

S$)

Dialing

(0$)

PART

II.

REFERENCE

APPENDIX

A-Error

/Flow Control Concepts

Overview

Throughput
MNP

Service Classes
Error Detection /Retransmission
Flow Control

Example

I-Transmit

Data

Example

2-Received

Data

APPENDIX

B-Summaries

and Tables

The RS-232C Interface, with Pin Definitions

Front End Indicators

DIP

Switch Summary

Default Settings

S-Register Summary
ASCII Chart

APPENDIX

C-Alphabetic

al Command Summary

APPENDIX

0-Problems

and Solutions

If

You Still Have Problems

APPENDIX

E-Additional

Operational Information

Using Both Voice and Data Communications
High Speed/Low Speed Protocol

Retrain Sequence

PBX,

Dedicated Line, and Leased Line Operations

Hewlett Packard Installations

APPENDIX

F-Technical

Specifications

GLOSSARY

INDEX

7-4
7-4
7-4

7-5
7-5

7-6

A-1
A-1

A-1
A-1

A-2
A-3

A-4

A-4
B-1

B-1

. I

B-2. I
B-3.

I

8-4.

I

B-5. I
B-6. I

C-1

D-1

0-3

E-1

E-1

. I

E-2.

I

E-3. l

E-4. 1

E-5. I

F-1

G-1

LIMITED

WARRANTY

COURIER HST

U.S. Robotics. Inc .. warrants to the original

consumer

or

other

end user purchaser that this product

is

free from

defects

in

materials

or

workmanship

for a period

of

two

years from the date

of

purchase. During the warranty period.

and upon

proof

of

purchase, the product will be repaired

or

replaced (with the same

or

similar model) at

our

option.

without charge for either parts

or

labor. This warranty shall

not apply

if

the product

is

modified, tampered with. mis-

used.

or

subjected to abnormal working conditions.

REPAIR

OR

REPLACEMENT

AS

PROVIDED UNDER

THIS

WARRANTY

IS

THE

EXCLUSIVE REMEDY

OF

THE

PURCHASER.

THIS

WARRANTY

IS

IN

LIEU

OF

ALL

OTHER

WARRANTIES. EXPRESS

OR

IM-

PLIED,

INCLUDING ANY

IMPLIED

WARRANTY

OF MERCHANT ABILITY

OR

FITNESS

FOR

A

PAR-

TICULAR

USE

OR

PURPOSE.

AND

U.S.

ROBOTICS

SHALL

IN

NO

EVENT

BE

LIABLE

TO

PURCHASER

FOR

INDIRECT

OR

CONSEQUENTIAL DAMAGES

OF

ANY

KIND

OR

CHARACTER.

Some states do not allow the exclusion

or

limitation

of

inci-

dental

or

consequential

damages

or

allow limitations on how

long an implied warranty lasts, so the above limitations

or

exclusion may not apply to you. This warranty gives you

specific legal rights, and you may also have

other

rights

which vary from state to state.
To

obtain service under this warranty. contact the U .S.

Robotics Technical Support Department at

800

/982-5151

(in Illinois, 312/

982-5151),

or

by mail at 8100 North

McCormick

Blvd.,

Skokie, Illinois. 60076. You will be

given a Return Materials Authorization

(RMA)

number

to

help us keep track

of

your warranty request.

Once

you have

received your

RMA

number,

take

or

mail the product, post­age prepaid, to U.S. Robotics at the above address. Include
proof

of

the date

of

purchase. IMPORTANT: If you ship

your unit, pack it securely, be sure your

RMA

number

is

visible on the outside

of

the

package,

and ship it charges

prepaid and insured.

>-

Should you

encounter

problems in operating this device.

follow the instructions in Appendix D in Part lI

of

this man-

ual.

The

Appendix contains solutions to operating problems

as well as procedures to follow

if

there

is

an apparent

modem

malfunction.

vii

COURIER HST

FCC

REGISTRATION

viii

CONNECTING

TO THE

TELEPHONE

COMPANY

FCC68: CJE794- l l

323-DM

-E

RINGER

EQUIVALENCE:

048

FCCl5:

CJE

794FAST

It

is

not necessary to notify the teleph one

comp

any before

in

stalling the

modem

.

Howev

er. the telephone

co

mpany may

request the telephon e number(s) to which the Couri er

is

con-

nected and the FCC inform ation printed above.
If the telephone co

mp

any has any ques

ti

ons

or

raises prob-

lems, ask them to

ca

ll

the T

ec

hnical

Supp

o

rt

Department.

USRobotics. Inc .. 800/982-5151 (in Illinois. 312/982-5151).

If the mod em

is

malfunctioning.

it

may affect the telephon e

lines. In this

case.

dis

connect

the mod em until the source

of

the diffi culty

is

traced. Do not use the mo

dem

on party

or

co

in

telephone lines.

RADIO

AND

TELEVISION

INTERFERENCE

COURIER HST

This equipment generates and uses radio frequency energy
and if not installed and used properly.

in

strict accordance

with the

manufacturer's

instructions, may cause interference

to radio and television reception. The Courier

HST

has been

tested and found to comply with the limits for a Class B
computing device

in

accordance with the specifications

in

Subpart

J

of

Part

15

of

FCC

rules. which are designed to

provide reasonable protection against such interference in
a residential installation.

However, there

is

no guarantee that interference will not

occur

in

a particular installation.

If

this device does cause

interference to radio

or

television reception, which you can

determine by monitoring reception when the modem

is

on

and off, try to correct the problem with one

or

more

of

the

following measures.

Reorient the receiving antenna.
Relocate the

computer

with respect to the receiver.

Relocate the

computer

and/or the receiver so that they are

on separate branch circuits.

If necessary, consult your dealer

or

an experienced radio/

television technician for additional suggestions. You may

find the following booklet , prepared by the Federal

Commu-

nications

Commission,

helpful:

How to Identify and Resolve Radio-TV Interference

Problems

Stock No.

004-000-0345-4

U.S.

Government

Printing Office

Washington,

DC

20402

ix

COURIER HST

X

FOR

CANADIAN

MODEM

USERS

Th

e

Canadian

Department

of

Communication

s (DOC) label

identifies certifi ed equipment. This certificati on m

ea

ns that

the e

quipment

m

ee

ts

ce

rtain tel

eco

mmunications network

protective,

op

erational, and

saf

ety requirements.

Th

e depart-

ment

does

not guarantee the

equipment

will

op

erate to a

user's satisfaction.
B

efo

re installin g th is e

quipm

ent , ma

ke

sure you are permit-

ted to

connect

it

to the facilities of the local tel

eco

mmuni-

ca

ti

ons

compan

y. You must also install the equipm ent using

an acce ptable

method

of

connec

ti

on. In some case s, you

may also extend the c

ompan

y's

in

s

id

e wiring

fo

r s

in

g

le

line

individual ser v

ic

e by mean s

of

a ce rtified connec tor ass

em

-

bl

y (tele

phone

extension cord ). You should be a

war

e, how-

ev

er

. that compli ance with the above conditions may not

pr

event degradati on

of

service

in

some

situations.

Repairs to certified e

quipment

should be made by an author-

ized

Ca

nadian maintenance facility des ignated by the sup-

plier. An y repairs

or

alterations made by a use r to this

e

quipm

ent,

or

e

quipm

ent malfun c

ti

ons. may give the

tel

eco

mmunicati ons co

mpany

ca

use to request the us

er

to disconnect the equipment.
Fo

r your own protec

ti

on, make sure that the elec tric

al

ground connec

ti

ons of the

pow

er utility. telephone lines,

and internal metallic water pipe system,

if

present, are con-

nected together. This precaution may be particularly

impor

-

tant

in

rural areas.

CAU

TION:

Do not attempt to make such

co

nn

ec

ti

ons

yourself;

conta

ct the appropriate electric inspec

ti

on authority

or electrician.

Courier

HST Modern L

oa

d Numb er: 388

Th

e Load

Numb

er (LN) assigned to each terminal device

denotes the perce

nt

age

of

the total load to be co nnected to

the telephone l

oo

p used by the de

vi

ce. without overloading.

The termination on a loop may

co

nsist

of

an y combination

of devices. subject o

nl

y to the re

quir

ement that the total

of

the Load

Numb

ers

of

a

ll

the devices not exceed I 00 . An

alphabetic suffix is also specified

in

the Load N

umber

for

the appropriat e ringing type (A

or

8).

if

appli ca

bl

e.

For

example. LN

=

38 8 designates a Load

Numb

er

of

38 and

a 8 -type rin

ge

r.

HOW

TO USE

THIS

MANUAL

COURIER HST

This manual

is

divided into two parts. The first part

is

designed to aid you

in

getting your modem connected and

operating as quickly as possibl e. Part I

al

so includ es chap-

ters on

command

usage. Part

II

contains a number

of

informative appendixes that you may

or

may not nee d,

depending on your situation. plus a Glossary and Index.

Below

is

a brief description

of

the

manual's

contents. We

suggest you review at least Chapters

1-3

before operating

th

e modem.

• Chapter

I-Introduction

• Chapter

2-Assembling

and testing the modem

• Chapter

3-lmmediate

operations-essentials

• Chapter

4-Interface

controls

•

Chapter

5-Internal

controls

• Chapter

6-Calling,

answering and disconnecting

• Chapter

7-Inquiries

and Help screens

The appendixes in Pa

rt

II

cover

the following subjects:

• Background information on error and flow control

• Summaries and tables

• Problems, their causes, and solutions

• Additional operational information

• Technical specifications

Whenever a cross-reference

is

made to the same

or

a similar

subject,

you'

II

be directed to the appropriate section

of

the

manual with this arrowhead symbol,

~

xi

USR-HST

Trellis

Coded

Modulation

Asymmetric

Modulation

Enhanced

Error

Control

Shorter

Response

Time

THE COURIER

PRODUCT

FAMILY

MNP

Error

Control

at

2400/1200 BPS

COURIER HST

CHAPTER 1

INTRODUCTION

The USRobotics Courier HST modem represents powerful,
advanced electronic design that gives you optimal speed and
accuracy. USRobotics' High Speed Technology (USR-HST)
offers these advantages:

Trellis coded modulation

is

a convolutional coding technique
that makes data transmission less vulnerable to errors caused
by

phone network impairments.

It

can tolerate twice the tel­ephone channel noise power as conventional modulation
(quadrature amplitude modulation,

or

QAM), so there are

fewer error-control retransmissions. Trellis coded modula­tion

is

also less susceptible to impulse-type noise.

At top speed, data flows

in

one direction at 9600 bits per

second and

at

300 bits per second

in

the other. The modems

automatically switch the high-speed channel on demand,

i.e.,

depending on which transmitter has the most data to
transmit. In practice, the modems seldom need to reverse
channels, since the asymmetric design reflects typical com-

munications sessions- brief messages typed at one end

of
the link, files sent from the other. The asymmetric approach
provides the most efficient and economical strategy for using
ordinary phone channels

at

high speeds.

The

HST

error control protocol uses sophisticated error
detection methods to ensure data integrity. Design effi­ciencies have reduced the overhead (extra control infor­mation) experienced with error control protocols at lower
speeds. On local and long-distance connections the result
is

accuracy. greater speed and higher

throughput-

approximately 1100 characters per second.

9600-bps modems are generally most efficient for file trans­fers. You'll find that the Courier HST also offers faster
response times during interactive sessions.

In addition to the Courier

HST's

new features, the modem

incorporates the same popular capabilities

of

other products

in

the Courier line:

The Courier HST implements the Microcom Networking
Protocol

(MNP), Service Classes

l,

2, and 3, at 2400 and

l 200 bits per second. This ensures compatibility with the
Courier 2400e and other MNP-compatible modems at
those speeds.

1-1

COURIER HST

Data Rate

Fall back

Inactivity

Timer

Call

Duration

Reporting

Ca

11

Progress

Detection

Modem

Settings

Display

HELP

Screens

Bottom

Panel

Reference

Repeat

Commands

Quote

Mode

Adaptive

Dialing

1-2

Automatic
Retraining

The

Courier

HST

automatically falls back to 2400. 1200.

and

300

bits

per

second . in both

Originate

and

Answer

Modes, to match a lower rate

of

a called

or

calling

modem.

You can optionally set local interface and link rates at
fixed speeds.

You

can

set the

modem

to automatically

hang

up after a

specified

number

of

minutes if there is no activity

on

the

phone

line.

The

modem

records the duration

of

your

calls in hours,

minutes,

and

seconds.

This

feature

enables

you to display

and print an audit

of

your

calling activities. You can option-

ally use the

modem

clock

as a real-time clock.

An optional set

of

result

codes

(screen messages) lets you

know

when

a line

is

busy, a person rather than a

modem

has

answered

the

phone,

there

is

no dial tone,

or

the distant

phone

is ringing.

On

command,

the

modem

displays its current settings, a

handy way to

check

your

transmission rate, S-registers and

other

operational controls.

You

can

also

displa

y screens that

summarize

the

command

sets. Dial

command

options,

and S-register functions.

Operational

summaries

and

other

information are printed

on

the

bottom

of

the

modem

case. A Dual In-Linc

Package

( DIP) switch guide

makes

it

easy to tailor the switch set-

tings to

your

requirements.

You can have the

modem

continuously repeat a

command

until you instruct

it

otherwise.

This

is

especially useful in

dialing services

whose

lines are often busy.

Set the

modem

to

Quote

Mode

if

you want

it

to dial

an alphabetic

"number,"

such as

800-"DIAL

USR"

(USRobotics'

Sales

Department).

You

can

set the

modem

to first try

Touch-Tone

dialing.

If

tone dialing

doesn

't work

on

the line. the

modem

automatic-

ally

switches

to the

slower

type,

pulse (rotary).

Retraining

(a

resynchronization with the remote

modem)

occurs

if

the

modem

detects line disturbances that might

affect

data

reliability. At

9600

bps the

connection

must be

with an

HST-compatible

modem.

Retraining also

occurs

at

COURIER

HST

COMPATIBILITY

COURIER HST

2400 bps if the

other

modem

is

Y.22bis-compatible.

(>

Ap-

pendix E-3 contains more information.)
The

Courier

HST

offers upgrading to

9600

bps while main-

taining compatibility with most installed 2400/

I

200/300 bps.
dial-up modems and existing software. Its compatibility
features include the following:

• Can be used with any

computer

or

terminal that

is

compatible with the RS-232C standard interface.

(>

For more information on the

RS-232C

interface.

see Appendix

8-

I . )

• Can be used with

any

computer

or

terminal that uses

ASCII,

the standard character code supported by most

equipment

manufacturers.

•

Connects

with any

modem

whose signal

scheme

is

compatible

with the following standards at the given

data

rate:

300

bps

1200 bps

2400

bps

9600

bps

Bell

!03

Bell 212A

V.22bis

USR-HST

• Uses the

HST

error

control protocol at

9600

bps

and.

optionally. the

MNP

error

control protocol, Service

Classes

I.

2

and 3 at

2400/1200

bps.

•

Is

fully FCC-certified for the uses described in this

manual.

1-3

PACKAGE

COMPONENTS

OPERATIONAL

REQUIREMENTS

COURIER HST

CHAPTER 2

SET-UP AND TESTING

Figure 2.

]-Courier

HST

The

box

containin

g

yo

ur

Courier

HST

contains

the following

it

ems in additi

on

to this

manu

al:

•

The

Courier

HST

mod

em

• An

RJ

I IC

phone

cord

• A

power

adapter

• A

Quick-R

efe

rence

card

,

in

the

manu

al

•

Your

warranty

card,

to be filled

out

and returned to

U

SRoboti

cs.

Inc.

The

Courier

HST

has

minimal

operational

requirements.

Be

sure to read th e

information

in the front

of

this

manual

about

radio

and

television interference

and

connecting

to the

phon

e

co

mpany.

In

addition.

you

should be

aware

of

the following:

•

Follow

the

operating

instructions in

Appendix

E-4

if

the

mod

em is to be used in

either

of

the following

types

of

in

stallation.

I

J

The

modem

will be installed in a k

ey

system

PBX

in

which

RJ

12

or

RJ

13

telephon e

ja

cks

are used

rather than the

RJ

I I jack.

2)

The

modem

will be attached to a use r-installed

phone line

or

a line l

ease

d from the

telephone

company.

Often

r

efe

rred to as

"dedi

ca

ted"

or

"private

...

this type of line is used for a

dir

ec

t.

2-1

COURIER HST

2-2

ASSEMBLING

THE

MODEM

continuous connection between two modems.
The connection

is

made without dialing.

•

If

the modem

is

installed in a Hewlett Packard system,

be sure to follow the instructions

in

Appendix E-5.

•

If

you're working with a computer rather than a ter-

minal, the computer must be in Terminal Mode.

If

you're not familiar with this requirement, check the

Glossary and refer to your communications software

documentation for instructions.

• You'll need an RS-232C cable to connect the modem
to your computer or terminal.

It should be a shielded

cable to ensure minimal interference with radio and
television reception. (~ For information on the RS­232C interface, see Appendix B-1.)

The modem takes a DB-25P (25-pin plug) connector,
but computer equipment varies: check the serial port
at the rear

of

your machine. The port will be labeled

"Modem,"

"Communications,"

or

"EIA,"

or

with a

phone symbol. (Don't use the port marked

"Printer"

or

"Aux.")

If

the port

is

a plug, specify a DB-25S

(socket) connector to your dealer.

If the port

is

a

socket, specify a DB-25P (plug) connector. If your

machine has other than a 25-pin port, check your

documentation to see what type

of

RS-232C con-

nector

is

required.

I. Turn

off

the computer

or

terminal and its peripheral

devices.

2.

Examine the label on the bottom

of

the modem.

In

addi­tion to the summaries and other information, the label
contains icons to aid

in

modem assembly. Then check

the interfaces at the back

of

the modem, shown in the

following photograph.

COURIER HST

Figure

2.2-lnterface

End, Courier HST

3.

Now

review the attached interfaces

in

Figure

2.3.

Figure

2.3-Connected

Courier HST

4. Check to make sure that the

power

switch

is

OFF; press

it

towards the zero in the

l/0

icon on the bottom label.

Then

plug the small end

of

the

power

supply cord into

the power jack at the back

of

the modem, and plug the

power

adapter into a standard 115-volts AC wall socket.

2-3

COURIER HST

2-4

Disconnect your present phone cable from the wall jack.
Plug one end

of

the phone cord that came with the

modem into the wall

jack,

and the other end into one

of

the phone jacks at the rear

of

the modem.

NOTE: Older telephone installations may not have the

appropriate modular wall jack and plug. Adapters and

RJ

11

C connectors are available from your telephone

company

or

computer dealer.

If

you want to keep your telephone connected for conven-

tional calls, plug its cord into the other jack at the rear

of

the modem. You can also use both your telephone and
modem

in

one call, although not at the same time.

>

Ap-

pendix E-1,

"Using

Both Voice and Data Communica-

tions,''

explains how to switch control

of

the phone line

between the modem and the phone.

5. Next, check the positions

of

the bank

of

Dual In-Line

Package (DIP) Switches located at the back

of

the
modem. These switches are set at the factory to the posi­tions desired by most users, as shown in Figure 2.4.

QUAD 1 2

3

4 5 6

7

8 9

10

o;~

IL:::::,

~

1

1

~l..'.:...ll

~

I~~

I

~::'..L:.I

~~I~

1....'.:::'..l..~

I

~~I

~~I~

I

Figure

2.4-DIP

Switch Factory Settings

>

Use the guide on the bottom

of

the modem or refer to

the more detailed summary in Appendix

8-4

to determine

if

your situation requires a different setting.

If

you're

connecting the modem to a dedicated line or to a small

interoffice

or

PBX system, review Appendix E-4 for spe-

cial installation and operating instructions.

6. The final step

is

10

connect the modem to the com-

puter's

or terminal's serial port with the RS-232C cable

described earlier under

"Operational

Requirements."
Attach the appropriate connectors to the modem and to
the serial port.

N

OTE

: When you are using the modem, be sure not to

cover the vents on the top

of

the case.

The modem

is

now ready to be tested and operated.

TESTING

COURIER HST

To verify that your modem

is

working properly, follow

these steps:

I.

Tum

on your computer or terminal and clear the screen.
Then turn the Courier's power switch ON. These front
indicator LEDs will light

up:

HS

High speed: 9600 bits per second

CD Carrier Detect (if you haven't changed the

factory setting

of

DIP switch 6)

TR Data Terminal Ready (if you haven't changed

the factory setting

of

DIP switch

I)

MR Modem Ready/Power
RS

Request to Send, if your computer/terminal
supports RTS on the RS-232C interface

CS Clear to Send

2.

If

you're

using a personal computer, load your tele-

communications software and put your computer

in

Ter­minal Mode. This causes the computer to function as a
terminal rather than a processor: everything you type at
the keyboard goes directly to the modem.

If

necessary,
refer to your communications software documentation
for instructions.

3. Next, check to see

if

your machine and modem are com­municating with each other by entering the command
to get the

modem's

"attention."

(Type either upper

or
lower case letters, not a combination. In this manual,
the Carriage Return

or

Enter key required to issue com-

mands

is

represented by the symbol

<er>.

Don't

type

the angle brackets.)
Type the following:

AT

<er>

If

everything

is

correct, the modem responds as follows:

OK

NOTE: The AT command

is

used alone to check the

modem/terminal interface. AT

is

also the mandatory

prefix for all other commands except A/ and

A>,

used to

repeat execution

of

the command in the command buffer,

and

+ + +, the escape code. These exceptions are

explained in Chapter 6.

2-5

COURIER HST

Analog

Loopbaek

Self-Test

2-6

4.

The

modem

is

shipped with DIP switch 4 UP. causing

the mod em to display (echo) your keyboard

commands.

If y

our

typed co

mm

and is not displa yed . y

our

l

oca

l ech o

is

OFF

. To turn the local ec ho

ON.

send the modem the

followin g

command.

ATE1

<

er

.->

If

double characters

appear

on the sc

re

en. both y

our

modem

and softw are are set to local echo

ON.

Either set

y

our

so

ft

ware to local

ech

o

OFF.

or

turn the mo

dem's

echo

OFF

with this

command

:

ATEO

<-

er

>

S.

If no

OK

a

ppear

s on y

our

screen. check out the

connec

-

tions at the interface

end

of the modem.

Then

ca

refully

review the previous instructions to see if you 've missed

s

omethin

g.

Another

way to verify that the

modem

is working properly

is to run this test. During Anal

og

Loopb

ack the modem

modulates and

demodulate

s dat a sent to it. and returns the

data to the screen. Follow these steps:

I. Because modulation at

9600

bps

is

asymmetric. the

self

-

test must be performed at 2

400

bps and below.

The

first

step

is

to

set your terminal or softw are to

2400

bps.

2.

The

mode

m·s

defa ult error

co

ntrol setting

is

&M4.

But

if the mo

dem

is

se t for error control (

&M4

or

&MS)

you wo

n't

be able to tell if there

is

a problem with the

modem

's transmitter

or

rec eiver, as

it

will retransmit any

errored data. For this reason, the following

command

sets

the modem to Normal Mode

(&M0)

before issuing the

command

for the test

(Sl6=5D).

The

t

es

t option caus

es

the

modem

to modulate and

demodul

ate its internal test pattern at the Origin ate (dial)

frequency and return the pattern to the screen. (Spaces

in

c

omm

ands arc unnec

essar

y, but are included

in

this man-

ual for r

ea

dability. ) Type:

AT

&MO

S16

=

5D

<

er

,

When

the

modem

enters Anal og Loopback Mode the

AL

indicator at the

fr

ont

of

the

modem

li

ghts. The mo

dem

g

oes

of

f ho

ok

(the equival ent

of

picking up a phone

Additional

Test

Procedures

COURIER HST

receiver), sends the message

CONNECT

2400 to the

screen. and then sends the test pattern.

3. Press any character key to terminate the test.

The

modem

goes back

on hook

(the equivalent

of

hanging up the

phone). and responds with the message NO CARRIER.

4.

Follow the same steps if you want to test the Answer
frequency, but substitute the Answer command (A) for
the Dial command (D).

If

you've

already set the modem

for Normal Mode, as

in

Step

2

above, you don't need to

type

&M0

again:

AT

&M0

S16

=

5A

<

er

>

5.

Reset your terminal

or

software to 9600 bps. Reset the

modem to its error control and Data Mode defaults with

this command:

AT

&M4

S16

= 0

<

er

>

You may want to take the time at this point to read the

following information on other test options, or skip

to

Chapter 3 for basic operational guidelines.

S-register

16

has five settings, explained in what follows.

0

I

2

Data Mode (no testing)
Analog Loopback
Dial Test

4 Test Pattern

5 Analog Loopback with Test Pattern

I.

To

perform analog loopback testing

of

the Originate or

Answer frequency without the test pattern, set the ter­minal or software to 2400 bps and issue either

of

the

following commands:

AT

&MO

S16

=

10

<

er

>

AT

&M0

S16

=

1A

<

er

>

The modem enters Analog Loopback Mode, goes

off

hook and displays the message

CONNECT

2400.

Type any message you wish at the keyboard.

It

is looped

through the modem and returned to the screen.
End the test by not typing anything for

at

least one sec-

ond and then typing three pluses. This

is

an escape code

2-7

COURIER HST

2-8

that forces the modem back to Command Mode

(don't

type the AT prefix or enter a Carriage Return):

+++

The modem returns the OK message.
To have the modem exit Analog Loopback Mode and

hang up the phone. first reset your transmission rate to
9600 bps. Then reset the modem to its error control and
Data Mode defaults with this command:

AT

&M4

S16=0

<er

2. The Dial Test is used to test the frequencies

of

Touch-

Tone values.

If

S16

is

set to 2 and a single Touch-Tone

is

dialed

(e.g.,

ATDT7

<er>),

the modem continues

to transmit that tone until another Carriage Return is

entered. This test

is

used

in

factory testing.

3. The Test Pattern alone

(ATS16=4

<er>)

is

used for

testing equipment and the phone line.

If

S

16

is

set to 4
and a Dial command issued, the modem transmits the test
pattern upon connection to the remote system. If set for
Auto Answer (DIP switch 5 UP). the modem transmits

the test pattern when

it

answers a call.

4. The preceding instructions test the modem at 2400 bps.
To test the modem

at

1200 or 300 bps, set your termi­nal or software to the lower speed and follow the same
procedures.

5.

It

might happen that you have issued either S

16

= I or 5

and the modem

is

in

Analog Loopback Mode, but you

haven't

yet sent a Dial or Answer command to initiate

testing.

If

the modem

is

also set for Auto Answer and a

call comes in, the Courier

HST

resets S

16

to zero and

answers the call.

NOTE: After any testing, be sure to reset S-register

16

for
normal Data Mode operations, with or without the default
error control setting (&M4):

ATS16=0

<er>

DATA FORMAT

ERROR

CONTROL

&MO
&M4

&M5

DIALING

HST-Compatible,

9600

bps

MNP-

Compatib/e,

2400

or

1200

bps

COURIER HST

CHAPTER 3

OPERATIONS

AT

A GLANCE

Here are some brief guidelines for immediate operation

of

the modem.
Ten-bit data units: check the table on page

6-1

or page

F-1

.

Both modems

must

be set to error control mode for error

detection and retransmission to occur.

Alwavs use error

control

for

9600-hps communications.

We use the term ARQ (automatic repeat request) for error

control. The three ARQ settings are as follows:

Normal Mode. No error control.
Normal/ARQ

Mode-Default.

The Courier attempts an ARQ

connection;

if

the signal isn't recognized. the modem contin-

ues

in

Normal Mode (&M0).

ARQ Mode. The Courier attempts an ARQ connection: if
the signal isn't recognized, the modem hangs up.

Use these settings/commands to call the following types

of

modems at the indicated speeds.
Terminal /software: 19.2k (preferable) or 9600 bps
Type:

AT

&H3

D

phone

number

<

er>

The command includes the setting for hardware/software

flow control ( &H3). See the flow control guidelines that
follow. 1f the modem isn't set for error control, include
&M4 or &MS

in

the command line.
Terminal/software: 19.2k, 9600, 2400 or 1200 bps
Type:

AT

&H3

D

phone

number

<

er

>

The command includes the setting for hardware/software

flow control (&H3). See the flow control guidelines
that follow.

3-1

COURIER HST

Non-MNP

Compatible,

2400, 1200

or

300

bps

FLOW

CONTROL

MAXIMUM

THROUGHPUT

HIGH-SPEED

CHANNEL

TURNAROUND

LINK

NEGOTIATION

3-2

See the flow control guidelines that follow.
Terminal/software: 2400. 1200

or

300 bps

Type:

AT

&M0 D phone

number

<er>

NOTE:

&M0

suppresses the MNP signals that may be mis­interpreted by the remote system and prevent a successful
connection.

Hardware and/or software flow control can be used for
transmitted and received data. We recommend hardware

Transmit data flow control

(&HI)

since this setting

doesn't

affect the data stream. This is especially important

if

you're

transmitting binary data.

Use flow control

in

any

of

the following situations.

•

You're

using error control (9600/2400/1200 bps). Flow

control prevents buffer overflow

in

the event that line

disturbances cause frequent retransmissions.

• The rate at the local terminal interface is higher than
the link rate.

• The volume

of

data transfer

is

high.

Flow control commands are covered

in

Chapter 4.

Use these settings for both Originate and Answer Modes.

Terminal/software:

Modem:

19.2k bps

Fixed terminal interface rate

(&BI)

Variable link rate

(&N0)

Transmit Data flow control (

&H

1

preferred, &H2 or &H3)

As described

in

Chapter

I,

HST modems use asymmetric
modulation. The modems allocate the high-speed channel on
demand so that the modem with the greatest amount

of

data

in

its buffer transmits at 9600 bps. Turnaround

of

the chan-

nel is automatic and requires no user intervention.
When a Courier HST calls an HST-compatible modem and

both are operating at 9600 bps, the modems negotiate the

link connection

("shake

hands")

at 2400 bps and automatic­ally resume operation at 9600 bps. The lower handshaking
rate maintains compatibility with the existing telephone net­work as well as existing hardware and software.

DATA

RATE

DEFAULTS

NONVOLATILE

MEMORY

(NRAM)

PHONE

NUMBER

STORAGE

DIALING

STORED

NUMBERS

COURIER HST

It's possible for

two

HST-compatible modems to connect

directly at

9600.

without 2400-bps handshaking, but

hoth

modems

must be set as follows:

Terminal/software:

Modem:

9600

or

19.2k bps

Fixed link rate

of

9600

bps (&N6)

Error control. either

&M4

or

&MS

Terminal interface:

&80,

detect rate from the AT

command.

then follow connection

rate.

Link interface:

&N0

, negotiate the highest possible

rate with the remote modem

in

both

Originate and

Answer

Modes.

The terminal interface and link rates may be set to fixed
rates using

&8

I and

&Nl-6,

respectively.

The

modem

is factory set

(DIP

switch

IO

OFF) to load the

settings stored

in

NRAM

on

power

up. Write

your

own

configuration defaults to

NRAM

with the

&

W

command.

To

review the

NRAM

settings, refer to Appendix

8-3

or

type:

ATl5

<

er

'>

Use

&Zn

=

s

to store four frequently

ca

lled phone numbers

in

NRAM

(nonvolatile memory);

11

=

positions

0

through

3,

s

=

number-string.

The

string may contain a

maximum

of

36

characters and any Dial

command

options.

Example:

AT&Z

=

9,, 1 312 5551234

<

er

>

(Store at position 0)
Example :

AT&Z1

=

5551234

<

er

>

(Store at position I)
To

dial, issue the

DS11

command

, where

II

indicates the

position

of

the

number

in

NRAM.

Example:

ATDS

1

<

er>

(Dial

number

at position

1)

The first

command

in the following sequence stores the

phone

number

and access code for a long distance service.

The second

command

dials the stored

number

/access code

and continues dialing the long distance phone number.

AT&Z2

=

5551234,,9876

,,

<

er

>

ATDS2

D1

312

5556789

<

er

>

3-3

COURIER HST

BUSY

ANSWER

3-4

INACTIVITY

TIMER

Use A> instead

of

Al

and the modem redials up to

IO

tries

instead

of

once. Neither A> nor

Al

takes the

AT

prefix

or

a Carriage Return.
Add the Repeat Mode

command(

> ) to the Dial

command

string and the modem automatically redials up to

10

tries:

AT>

D5551234

<er

>

ATD5551234

> <

er

>

You may include the Repeat command when you store a
phone number-string

in

NRAM:

AT&Z2

=

5551234

> <

er

>

Set the inactivity timer (S-Register 19)

if

you suspect that
a connection may be inadvertently left open without data
transfer.

TERMINOLOGY

ERROR

CONTROL

ARO

Retry

Timer

COURIER HST

CHAPTER 4

INTERFACE CONTROLS

Use the

comm

ands explained

in

this chapter to select the

mode

m's

operating characteris

ti

cs at the terminal and link

interfaces. Th e

co

mmands apply to error and

fl

ow control,

and to the speed-select options at both interfaces.

)lo-

For

background informa

ti

on on

th

ese f

ea

ture s, see App endix A.

NOTE:

When

yo u change a defa ult settin g during a ses-

si

on. the mod em retains that setting until you do o

ne

of

th

e fo llowing:

• Select a n

ew

setting.

• Issue the Z

co

mmand to rel

oa

d the

NR

AM

defaults

or

the &F

co

mmand to l

oa

d the factor y settings.

•

Tum

the modem off.

For simplicit y. references to a

terminal

in

this chapter mean

bo

th

conventional terminals and

mi

crocomputers.

A

RQ

(a

ut

omatic rep

ea

t request. i.e. retransmission) is the term

used by USR obo

ti

cs in error

co

nt

rol commands and re-

sponse codes.
In

summ a

ri

es. the terminal is referred to as DTE, for Data

Terminal Equipment. while the mo

dem

is

referred to as

D

C£

, for Data

Co

mmunications Equipment. DTE/

DCE

indi-

cates the terminal/mo

dem

interface.

DCE/DC

E indicates the

link (modem -to-m odem) interface. (For

mor

e

in

fo

rmation

see

th

e Flow

Co

ntrol section

in

Appendix A.)

While error

co

nt

rol is option al.

it

should always be selected

fo

r

96

00

bps sessions.

The

USR-HST proto

co

l

is

used at

9600 bps. The

MNP

protocol is used at 2400 and 1200 bp s.

Bo

th

protocols use cyclic redundancy checking

fo

r error

detection. and an a

ut

omatic rep

ea

t request (ARQ ) for

retransmission

of

errored data frames.

It

may happen

th

at a retransmission request

fo

r

th

e same

frame occurs repeatedly. Ordinarily this is due to a serious
disturbance

in

the phone conn

ec

ti

on. The retry maximum is

12.

af

ter w

hi

ch the mo

dem

s a

ut

omatically hang up ins

te

ad

of

running up was t

ef

ul

phone charges.

If

the Co urier han gs

up and you

don't

know why, query register S20 with

this command:

ATS20?

<,

er -,

4-1

COURIER HST

4-2

Error

Control

Modes

(&Mn)

&M@

&M1-3

&M4

&M5

With

Auto

Answer

FLOW

CONTROL

COMMANDS

If

a

code

of

6 is

returned.

the

modems

reached

the retry

timeout

and

hung up. Place the call again: you'

ll

more

than

likely

ge

t a better

connection.

Und

er

error

control.

the

calling

mod

em

includes an

error

control request in its link negotiation signals.

The

answer-

ing

modem

may

or

may not recognize the request.

The

following

op

tions allow yo u to select a selling best suited

to

your

default

co

nfiguration as well as to indi

vi

dual calls.

No rmal

Co

uri

er

Mode.

no

error

control. Use this se lling

if

you're

ca

lling a n

on-MNP

modem

(2400

, 1200/

300

bps).

as the

error

control request

ma

y be

misinterpreted

by the

remot

e

system

and

prevent

a

connection.

Don·t

use this

setting for

9600-bps

calls.

These

options

are

reserved

for futur e use.

Normal /

ARQ

Mode.

If the

remote

modem

doesn't

recognize

the Courier"s

error-con

trol request, the

Cour

ier

automatically

operates

in

No

rmal

Mode

(&M0).

This

setting is the default.

Use this adaptiw

mode

if

error

control isn ·t

cruc

ial.

ARQ

Mode.

If the remote

modem

doesn

·1

recognize

the

error-control

request. the

Courier

HST

hangs

up. Use this

setting if

error

control is an absolut e requirement.

To

use

error

control for

incoming

calls.

set the

modem

for

Auto

Answer

and for

either

&M4

or

&M5.

When

calls

come

in

, the

Cour

ier

HST

goes

off

hook and

responds

to an

error-control request

if

one

is sent. If

th

e

Co

uri

er

doesn

·1

receiw

a request and is set to Normal /

ARQ

Mode

(&M4J.

it

answers

the

ca

ll

in

No rmal

Mod

e.

If

it

doesn

·t receive

a request and

is

set to

ARQ

Mode

(&MS).

it

hangs up.

Flow control

is

used to control the flow

uf

data input to

and

output

from the

modem.

to prev ent

data

loss.

For

more

information. refer to

Appendix

A.

The

Transmit

Data flow control

comm

and.

&H11,

controls

the flow

of

data

from the terminal to the

modem

.

Two

com-

mands

.

&In

and

&Rn.

control the

tlow

of

Received

Data.

Th

e factory-set default

of

the

Courier

HST

is

tlow

control

di

sab

l

ed.

As

mention

ed

in

Chapter

3.

flow

co

ntrol should

be enabl

ed

in the following situlltions.

• You·re using

error

control

(9600

/

2400/1200

bps).

If

you·re

transmitting and

problems

on

the line

cause

a

numher

of

retransmis sions. input from the

Transmit

Data

Flow

Control

(&Hn)

COURIER HST

terminal will back up and perhaps overflow the
modem's

buffer.

• The rate at the terminal interface differs from the link
rate, e.g. , the terminal's sending at 19. 2k bps and
the link rate is 9600 bps. This setup offers the great­est throughput, but the modem requires the ability
to signal the terminal when the

modem's

buffer is

reaching capacity.

• The volume

of

data transfer is high.

The modem monitors its buffer as data comes from the ter­minal.

If

the buffer approaches

90o/c

capacity, the modem
signals the terminal to stop sending. When the modem has
sent enough data over the link to half empty the buffer, it
signals the terminal to resume transmitting.

Two types

of

signals are used:

• Hardware: the modem raises or lowers the Clear To
Send (CTS) signal via Pin 5 on the RS-232C interface.

• Software: the modem sends the conventional ASCII
Transmit on/off (XON/XOFF) characters, as follows:

XON
XOFF

<Ctrl>-Q
<Ctrl>-S

(ASCII

17

Decimal,

11

Hex)

(ASCII

19

Decimal,

13

Hex)

The ASCII characters may be user-defined; see
S-registers S22 and S23 in Appendix B-5 and the
ASCII chart

in

Appendix B-6 or on the Quick-

Reference card.

'.\CHE:

If

possible, use hardware control as

it

is

more

efficient and doesn't affect the data stream.

&HO Flow control

of

transmitted data

is

disabled. This setting

is

the default.

&HT Use hardware flow control.

If

your terminal supports Clear
To Send (CTS. RS-232C Pin 5), the Courier lowers CTS
when the buffer nears

90o/c

capacity, and raises CTS again

when the buffer

is

about half full.

&H2

Use software flow control. The Courier sends the terminal

the XON/XOFF characters to control the input

of

data to

the buffer.

&H3

Use both hardware and software flow control. If you

are unsure about what your equipment supports, select
this option.

4-3

COURIER HST

Received

Data

Flow

Control

Modems operating

in

error-control mode automatically

control the

fl

ow

of data

on

the dat a link . Th e

co

mmands

described here

co

ntrol Received Data passe d by the

modem

to the termin a

l.

If the

data

rate at the terminal interface

is

9600

or

19.2k bp s, there may be a need at times to signal

the modem to te

mp

orarily stop passin g data. You may want

to try us

in

g one of the

two

following commands to set the

mode m to respond to flow control signals. The

modem

stops

the output

of

data to the screen and reta

in

s any data in the

buff

er until signaled to resume .

Software

Control

(&In)

If yo ur terminal suppo

rt

s the < Ctrl > -S and < Ctrl > -Q

com-

mands, yo u

ca

n use the &I

comm

and to set the mo

dem

to

respond to

XO

N/

XOFF

signals.

4-4

&I@

Disable XON/XO

FF

flow control of received data. This

option makes a

ll

characters, including co

nt

rol characters,

transpare

nt

to bo th modems. This setting is the default.

&17

Typing <

Ctr

l> -Sl< Ctrl> -Q caus es

XON !

XOFF

signals

to be sent to bo th

th

e lo

ca

l modem and the remote system.

If any data is

in

transit before the remote system stops

transmitting, the

Co

ur

ie

r saves the da ta

in

i

ts

buf

fe

r.

Thi s setting is espec ia

ll

y useful if you want to stop the

scrolling

of

in

com

in

g data so you can review it. When

the modem rece

iv

es the <

Crl

> -S, the data immediately

stops scrolling.

&12

Th e mod

em

acts on

XON

/

XOFF

si

gnals but doe

sn't

pass

them on to the remote system . This is a safeg uard

in

case

the remote system uses < any key>

in

st

ea

d

of

< Ctrl > -Q fo r

XON signaling. If a remote terminal has r

ece

ived an X

OFF

fr

om

it

s

ow

n modem.

it

will interpret your X

OF

F as < any

ke

y> , i

.e.,

XON .

and resume transmitting

da

ta.

&13

Hewlett Pac kard proto

col-Host

Mode. T

hi

s setting only

applies to modems attached to an HP ma

in

frame.

>

See

Appendi x E-5.

&/4

Hewlett Packard pro

tocol-Termin

al Mode. This setting

only applies to modems attached to t

er

minals

in

an

HP

system .

>

Sec App endi x E-5 .

Hardware

Control

(&Rn)

&RO
&RT

&R2

DATA

RATE

COMMANDS

Optional

Fixed Rates

COURIER HST

If

the terminal supports Request

To

Send (RTS)

on

the

RS-232C

interface (Pin 4) and RTS

is

not always high. the

terminal lowers RTS to signal the

modem

to stop passing

it

received data. and raises RTS when

it

is

ready to receive.

Reserved.
Ignore RTS. This

is

the default. This setting

is

required if

your terminal

does

not support RTS.

The

modem

only sends

data

to the terminal when RTS

is

high.

Two

commands

control the data rate at the terminal and link

interfaces,

&Bn

and

&Nn

,

respectively. At the default set-

tings

(&80.

&N0) the

modem

determines its rate

in

the

following ways:

• Initially the

modem

detects its rate from the rate at

which the terminal sends

it

the

AT

command

.

That

rate

is

determined by the terminal

or

software setting.

•

When

originating

or

answering a call, the

Courier

and

the remote

modem

negotiate the highest possible link

rate. For

example.

if the terminal sends the

AT

com-

mand at

9600

bps and the

Courier

calls a

modem

operating at 1200 bps, the

Courier

automatically falls

back to 1200 bps.

The

Courier

notifies the terminal

of

the adjustment by sending the result code

CONNECT

1200.

The

Courier

readjusts to

9600

bps at the next

AT

com-

mand

or

. if auto answering a call. readjusts to the rate

of

the incoming call.

>

See Appendix E-2 for more

details.

NOTE:

The

adjustments

occur

up to the rate ceiling set at

the terminal. If for some reason the terminal rate

is

set to

2400

bps and the

Courier

calls an HST-compatible operating

at

9600

bps. the remote

modem

drops

back

to establish a

2400-bps connection.
Optional speed settings allow you to fix the rate at either the

term inal

or

link interface.

or

both. These settings apply to

both normal and error-control operations. but

be sure to

enable Transmit Data ( &H)

flow

control.

4-5

COURIER HST

Terminal

Rate

Select

(&Bn)

&Bf!)

&81

Link Rate Select

(&Nn)

4-6

&Nf!)

&N1-6

Rate-Select

Guidelines

Use this command to select varying or fixed rates at the
terminal interface. Fixing a maximum rate at the terminal
interface offers greater efficiency, regardless

of

the modem

at

the remote end

of

a connection.

Variable rate: the terminal interface rate follows the connec­tion rate. Use this setting

if

your software switches its rate

when

it

receives the

CONNECT

result codes,

e.g.,

CON-

NECT 2400,

CONNECT

1200. The modem readjusts at the

next AT command or connection.
Fixed rate: allowable terminal/software settings are

l 9200/9600/2400/ 1200/300 bps. Setting the terminal to

19. 2k bps enables the greatest throughput.

~

See guideline

number 2 below.

If the &B and &N settings differ, be sure to use flow

control to prevent the possibility

of

data loss.

Normal operations: the link rate varies according to the

connection sequence.
Fixed link rate: the modem only connects if the remote

modem

is

also operating

at

the same rate. Allowable rates

are as follows:

&NI
&N2
&N3

300 bps

1200 bps

2400 bps

&N4
&NS
&N6

Reserved
Reserved
9600 bps

1.

Some software

doesn't

support a fixed terminal rate, but

always switches bit rates to the link rate established by
the modems during their connect sequence.

In

this case.

leave the Courier set to &B0.

2. For maximum throughput, use the settings recommended
in

Chapter 3 for both Originate and Answer Modes:

Terminal:

Modem:

19.2k bps

Fixed terminal interface rate

(&BI)

Variable link rate (&N0)

Transmit Data flow control

(&HI,

2, or 3)

3.

You can filter out calls at other than a specific speed, for
security or other reasons, by fixing the link rate.

4. If the Courier HST

is

connected to a mainframe, the
mainframe may require that the terminal and link rates
be fixed with the &B and &N commands.

DSR

OVERRIDE

(&Sn

)

&S(/)
&S1

COURIER HST

The Data Set Ready

(DSR)

function (Pin 6 on the

RS-232C

interface)

is

required on

some

sys tems to enable the

modem

to signal the t

er

minal when the

modem

is

ready to

answer

a

call. Typically.

DSR

signaling

is

overridden.

DSR

is

always

ON

(overridden). This setting

is

the default.

The modem controls DSR.

4-7

SETTING USING

DEFAULTS

Writ

ing Defaults

to

NRAM

(&W)

COURIER HST

CHAPTER 5

INTERNAL CONTROLS

Th

e

co

mm

ands explained in this cha

pt

er are

of

two types.

Th

e first group concerns default

co

nfig ura

ti

ons, for

example.

writing your own

power-on

defaults to nonvo latile

random

access m

emo

ry

(NRAM).

The

rem ainin g

co

mmands

are

used to sel

ec

t the

modem

's local operating characteristics.

for a current session

or

to include in

yo

ur

defa

ult c

onfigura

-

ti

on.

Th

ey include result

cod

e,

ec hoing . and other options.

:\

OTE:

Wh

en

yo

u chan

ge

a defa ult setting durin g a ses-

sion, the modem retains that settin g until

yo

u do

one

of

the

fo

ll

ow

ing:

•

Se

l

ec

t a new setting.

• Issue the

Z

command

to rel

oa

d

th

e

NRAM

defaults

or the

&F

command

to load the factory settings.

•

Turn

the mo

dem

off.

Th

e

Co

urier HST is s

hipped

from the factory with

it

s

sof

t

wa

re

defa

ults stored in r

ea

d o

nl

y memory

(

ROM

)

and

al

so

in progra

mm

able nonvolatile rand

om

access

me

mor

y

(N R

AM).

Th

e inclusion

of

NR AM a

ll

ows

yo

u to

program

your own co nfiguration

and

save the settin gs as y

our

power

-o

n d

efa

ults.

If

you store yo

ur

own

default

softw are settin gs in

NRAM,

the Courier l

oa

ds those settings when it is powered

on

if

DIP

switch 10 is UP (factory setting).

A

li

st

of

the settin gs s

tor

ed in NRAM is in Appendix

B-4.

You

ca

n al

so

dis

pl

ay the settin gs at any time by

se

l

ec

ting

option

5

of the

I

(inquiry)

comm

and:

ATl5

< c r >

If

yo u

've

sent the

modem

comm

ands to chan

ge

settings

throughout your session

and

want

to save

yo

ur

current

configura

ti

on, issue the

&W

comm

and:

AT&W

< e r >

You

ca

n also sp

ec

if

y y

our

configura

ti

on in a single

com-

mand string that includes the

&W

co

mm

and, as in this

example:

AT

X4

&B1

&M5

&H1

&11

M3

&W

<

er

>

5-1

COURIER HST

Loading

the

Factory

Defaults

(&F)

Resetting

to

NRAM

Defaults

(Z)

5-2

Storing

Telephone

Numbers

(&Zn=s)

Modify one

or

several settings

at

any time. for example:

AT

X7

&W

er

Factory defaults are permanently stored

in

read only mem-

ory

(ROM).

They

arc listed in the table

of

NRAM settings

in

Appendix B-4. You can set the modem to its factory

defaults during any session by typing:

AT&F

er

If DIP switch

IO

is

DOWN,

the factory settings are loaded

at

power

on instead

of

the NRAM defaults.

To reset the modem to its

NRAM defaults, type:

ATZ

er

'\OTL

On reset. the modem also checks the status

of

DIP

switches

2-

-5 and

9:

if

you change the setting

of

any

of

these switches when the modem

is

on. use the Z

command

to initiate the new setting( s).
The modem stores up to four frequently called phone

numbers. Write the numbers to

NRAM with the

&Zn=

s

command,

where

fl

is

position 0 through

3,

ands

is

the

number-string.
The number-string may be up to 36 characters long.

in-

cluding any Dial

command

options. The following example

includes the tone-dial (T) and

comma

pause options

of

the Dial

command.

The number

is

stored at position 0,

assumed because there

is

no

fl

parameter.

AT

& Z

•~

T 9 " 5 5 5 1 2 3 4 c r

The next example stores the phone number and

user's

access

code for a long distance phone service.

AT&Z1

5551234,,9876,,

er

Dial the stored number using the DSfl

command,

for exam-

ple. DS2

<er>.

Additional examples are

in

Chapter 6.

'\O

IE.

Don't

include

modem

settings in the

&Z

string. If

the call requires a special setting, insert the appropriate com­mand when you dial the stored number. In the following

RESULT CODES

Response

Modes

(Vn)

COURIER

HST

ex.ample.

&M0

(no error control)

is

substituted

fo

r the use r' s

error control default setting:

AT&MODS2

·

'--

Cr

•

Then reset the error control mode after the call, for ex.ample:

AT&M4

•,

cr

Four

commands

co

ntrol the result

cod

es the modem returns

to the scree

n:

Vn Nume

ri

c/verbal response mode

Xn

Result

co

de subset

Qn

Display/suppress a

ll

result codes

&

An

Display/suppre ss /

ARQ

res ult code s

Result

co

des are se

nt

to the screen

in

either words (Verbal
Mode) or numbers (Numeri c Mode). The Courier is factory
set to v

erb

al messages when

it

is powered on

(

DIP

sw itch 2

is UP) . Use the V

co

mmand to select

ve

rbal /num eric result

codes independently of the power-on default.

VCJ

Numeri c Mode. Numeri c result codes are foll owed by a Car­riage Return but no Line Feed, as in the following ex.ample.
where a 3 is returned (for

NO

CARRI

ER).

ATD1234567

<

er

>

becomes

3TD1234567

<er

>

V7

Verbal Mode. Verb al responses are preceded and fo llowe d

by a Carriage Return and a Line Feed. as in the

fo

llowing

ex.ample:

Resu It Code Sets

ATXCJ

ATX7

ATX2-7

ATD1234567

<

er

>

NO

CARRIER

A table

of

result code option s is on

th

e n

ex.

t page. The

format

of

the

comm

and

to

select a result code set is A

TXn

,

where

11

is a valu e from 0 through

7:

Basic sub set, returns the first five codes

(0-4

) in the

following table.
Ex.tended subset,

co

des

0-5

,

10

and

13

. Default. This set

adds rate-specific

CONNECT

messages to the Basic set.

These optio

ns

off

er advanc ed

ca

ll-progress code s and

functions.

5-3

COURIER

HST

5-4

Options

Summary

RESULT CODES

OPTIONS

TABLE

Commands

XO

X 1 X2

X3 X4

X5 X6

X7

Result Codes
0/0K

X X X X

X

X X X

1/CONNECT

X

X X X X X X X

2/RING

X

X X X X X X X

3/NO CARRIER X

X X X X X X X

4/ERROR X X

X X X X X X

5/CONNECT 1200 X X

X X

X X X

6/NO DIAL TONE X X X X
7/BUSY X X X X X
8/NO ANSWER

X X

X

X X

9/Reserved

10/CONNECT 2400

X X

X X

X X X

11/RINGING X X X
12/VOICE

X X

13/CONNECT 9600 X X X

X

X X X

Functions
Adaptive

Dialing

X X X

X

X X

Wait

for

2nd Dial

Tone

(W)

X

X

X X X

Wait

for

Answer

(Cu)

X X X X X

Fast Dial

X

X X X

I. An additional group

of

CONNECT messages (

15-17)

indicates

an

error-control connection with an HST- or

MNP-compatible modem.

>-

Seethe

"/ARQ

Result

Codes

(&An)"

later

in

this section.

2.

Adaptive dialing causes the modem to automatically use
Touch-Tone dialing and, if that doesn't work on the line,
revert to pulse dialing.

3. W and

@ are Dial options described

in

Chapter 6.

4. Fast dial causes the modem to dial

as

soon as a dial tone

is

detected, rather than wait the normal two seconds. If

there

is

no dial tone. the modem times out after 5 sec-

onds and sends the NO DIAL TONE (6) result.

5. After sending the BUSY

(7) result code, the modem

hangs up.

Quiet

Mode

(On)

O@

01

/ARO Result

Codes

(&An)

&A@

&Al

LOCAL ECHO

Command

Mode

Local Echo (En)

E@

El

COURIER HST

6. The NO ANSWER (8) result code

is

returned, instead

of

the standard NO

CARRIER.

when the

(i

-t

option

is

used

and there

is

no answer at the remote end.

7. After sending the VOICE (12) result code, indicating a
voice answer. the modem hangs up.

8.

X6 implements all result codes and functions. X7

includes all

of

X6 except the VOICE (

12)

result code.

Enable/suppress the display

of

result codes.

The

Courier

is
shipped with DIP switch 3 DOWN and defaults to display
ON when the modem

is

powered on. The commands here

control the display independently

of

the power-on default.
Result codes are displayed.
Result codes are suppressed (made

"quiet

"

).

This

is

useful

when the messages might interfere with the data stream.

If

these codes are enabled, one

of

the following results

is
sent to the screen when a successful HST or MNP connec­tion

is

established. (A setting

of

XI or higher is assumed.)

(15)

CONNECT

1200/

ARQ

(16)

CONNECT

2400/ARQ

(17)

CONNECT

9600/ARQ

/ ARQ codes are disabled. Some software does not allow the

/ARQ result codes.

In

this case. use this setting. Suppres-

sion

of

the / ARQ codes doesn · t affect the error control pro-

tocol; the modem returns the standard

CONNECT

messages.

/ARQ codes are displayed. This

is

the default.

Two

commands control what the modem displays on the

screen.

The

En

command applies to when the modem

is

in

Command Mode. The

Fn

command applies to when the

modem

is

online to another system.

The

En

command

enables/disables the display

of

your typed
commands. If double characters appear on the screen. both
the

modem's

local echo and the software· s local echo are

on. The Courier

is

shipped with DIP switch 4 UP, for local

echo

ON

when the modem is powered on. The commands

here control the echo independently

of

the p

owe

r-on default.

Command Mode echo OFF.

The

modem does not display

keyboard commands.
Command Mode echo

ON.

5-5

COURIER HST

Online

Local

Echo (Fn)

F(JJ

F7

THE

AUDIO

MONITOR

Speaker

Control

(Mn)

5-6

This

com

mand

causes the mod

em

to display a

copy

of

the

data

it

is

transmitting to another system.

Many

systems,

h

owever,

return a

copy

of

received data. which

is

ca

lled a

remote echo.

If

the

modem's

online echo

is

ON

and there

is

remote

echoing,

double characters

appear

on the screen.

In

some

microcomputer

docum

entation the online

echo

set-

ting is called the ·

·Duplex··

setting. although the t

erm

is

not

technically accurate.
Online

echo

ON.

Sometimes

called

Half

Dupl ex. As the

m

odem

transmits

data

to a remot e system. it also sends a

copy

of

the data to the screen.

Online

echo

OFF.

Sometime s ca

ll

ed Full Dupl ex. This

is

the default.
The

modem's

speaker

enables you to monitor the dial-

connect

process. There are several ways to make use

of

this feature. After the

Courier

H

ST

dials a

numb

er,

it

waits

30

seconds for a

hi

gh-pitched

answer

tone from the other

modem,

immedi ately followed by data signals. ca

ll

ed a

carrier.

These

signals must

occur

before a data link is

established.
If

someo

ne answers the phone, or if the line is busy. the

modem

sends the message NO

CARR

IER to your screen

after

30

seconds. If yo u listen to the speaker, you can

r

espond

immediat

ely instead

of

waiting for the

modem

to time out.
For

examp

le. if yo u h

ear

som

eo

ne

answer

ing the ca ll. you

mi

ght pick up the phone and ta

lk

to the person

or

ca

ncel the

call by pressing any key on the k

eyboa

rd. In the same way.

you

can

cancel a ca

ll

when you h

ea

r a busy signal.

You

ca

n also hear if dialing is proceeding too fast for the
syste m. Terminate the call (press any key) and reenter the
Dial co

mmand

with a

comma

or

two

to allow more time.
This ap plies to accessing an outside line (dialing 9, for
example) as well as to

checking

out whether a public serv-

ice has enough time to respond to yo ur account

number

or

other

code.

You

can

disable the speaker entirely

or

set the speaker to

monitor different segme nts

of

the dial-connect sequence.

COURIER HST

Mf!J

The

command

A

TM0

turns

th

e

speaker

OFF

entirely so that

you

don't

hear

the

modem

go

off

hook. dial. etc.

M

1

The

speaker

is

ON

until

Carrier Detect. This is the default

setting a

nd

lets you monitor call progress until the

Courier

detects the remote

modem's

carrier signals.

or

until the 30-

second timeout and result

code

displa y. At

Carrier

Detect.

the mod

em

disconnects the

speaker

and

data

transmission

sounds are suppressed.

M2

The s

peaker

is

ON

continuously, including durin g data

transmis sion.

M3

MODEM

CLOCK

USAGE

tKn)

The

speaker doesn't

go

ON

until after the last digit

is

dialed. then

goes

OFF

at Carrier Detect.

The

modem

clock

is

used as a call-duration timer

or

as a

real-time clock. Used

in

conjunction with the

111

(Inquiry)

command,

the

modem

returns the duration

of

the last call

in

hours. minutes. and seconds or the actual time.

Kf!J

Call-Duration Mode: the

modem

times ea ch call from

CON-

NECT

to NO

CARRIER.

and stores the information until

the next

co

nnection

or

the

modem

is

rese

t.

At A TI3

<e

r> .

the

modem

displays the

call's

duration.

If

you wish, you can

maintain a call log by printing this information after each

call. This setting is the default.

K 1

Real-Time Mode: the

clock

operates as a real-time clock

regardless

of

the pre sence

of

a carrier. Set the clock (mili-

tary time) by specifying the hour, minutes. and seconds as

in

the following

exa

mple, which sets the clock at the real

time

of

l

:3

0

p.m.

TRANSMITIER

ENABLE

DISABLE (Cn)

Cf!J

Cl

ATl3

13:

30

:

00

K1

er

At ATI3. the

modem

displays the real time. You'

ll

need to

set the clock each time you

power

on the

modem

, but the

clock

is

not affected by the reset

command,

ATZ.

If an additional terminal and

modem

share the phone line

for monitoring purposes, the sec

ond

modem

is placed

in

Receive

Only

state by disabling its transmitter.

Transmitter disabled.

Modem

is

set to Receive Only.

Transmitter

enabled.

This

is the default.

5-7

COURIER HST

5-8

BREAK

HANDLING

(&Yn)

&Y@

&YT

&Y2

&Y3

THE

S-REGISTERS

The Courier

HST

allows you to send a break to abort data

transfer without disconnecting from the data link.

The

following options are available.
Destructive, no Break transmitted: the modem clears the

data from its transmit buffer (all data

is

lost) but does not

pass on the Break to the remote modem.
Destructive, expedited: the modem clears the buffer and

immediately sends a Break to the remote modem. This

is

the default setting.
Nondestructive. expedited: the modem retains buffer data.

but immediately sends a Break to the remote modem.

Nondestructive, unexpedited (send Break

in

sequence): the

modem transmits any buffer data received before the Break,
sends the Break, and then sends any subsequent input from
the computer

or

terminal.

The S-Registers are used to set various timing parameters
and other operations. including redefinition

of

selected

ASCII characters. The defaults typify the requirements

of

most users.

~

A detailed summary

of

the S-Register functions

is

in

Appendix B-5. Less detailed summaries are on the bottom

label

of

the modem case and in the Quick-Reference card.

BASIC

REQUIREMENTS

Transmission

Rate

Error

Control

COURIER HST

CHAPTER 6

DIALING AND ANSWERING

To successfully establish a communications link, the called

or calling modem must be compatible with the following

standards

at

the specified bit rates.

Bits per

Second

9600
2400

1200

300

Standard

USR-HST or compatible

CCITT V.22bis

Bell 212A
Bell

103

To successfully exchange data, both modems must use
the same

I 0-bit data format. The formats allowed are

as

follows:

Start

Data

Bits Bits

7

7

8

Parity

Even, Odd,
Mark, Space
None, Even. Odd.
Mark, Space
None

Stop

Bits

2

1,2

In general, you should know the transmission rate

of

the

other modem before calling. However,

if

the link rate

is

set
to the default, &N0, and the Courier HST tries to connect
with a modem operating at a lower rate, the Courier falls
back to the rate

of

the remote modem. This applies to both

Originate and Answer Modes.

> See the discussion under

"Data

Rate

Commands,"

in Chapter 4.

Always set the Courier HST for error control. &M4 (the
default) or

&MS, for 9600 bps connections.

It helps to know

if

the remote modem is MNP-compatible at
2400/1200 bps. Some public network services, for example,
are not. When the Courier

HST

is set to &M4 it includes

an error-control link request in its handshake signals.

If the

remote modem

isn't

under error control, the Courier oper-

ates

in

Normal Mode (no error control). However,

if

the

remote modem

doesn't

support the MNP protocol at 2400

6-1

COURIER HST

Automatic

Retrain

PLACING

CALLS

6-2

Dial (D)

Dialing

Type

(P,

T)

or

1200

bps,

the

MNP

link-request signals may be misinter-

preted

and

block a successful

connection.

If you

know

the

remote

modem

doesn't

support MNP.

we

recommend

setting

the

Courier

HST

to

&M0

before dialing.

An

HST

or

V. 22his

modem

sends

a retrain signal

if

it

senses that a

problem

in the

phone

line

connection

may

be

causing

data

unreliability.

The

modems

stop the transfer

of

data

for about a

second

while they

resynchronize.

and

then

resume

Data

Mode

operation.

Retraining

only

occurs

during

9600

and 2400 bps

communi-

cations. >

For

a description

of

the signaling

sequence,

see

Appendix

E-3.

The

commands

discussed

in this section are used in the

following operations:

Dialing D (0-9

# * . ; !

PT

W

(1.1

R).

DS11

Redialing

A/,

A>.

>

Canceling

dialing

<any

key>

When

the Dial

command

is issued the

modem

goes

off

hook-the

equivalent

of

your

picking

up the

phone-then

enters

Originate

Mode

and dials the

number

sequence

that

follows.

The

modem

also

executes

any

other

commands

or

options

included in the

command

line.

The

command

string may include up to

40

characters, plus

the

AT

prefix

and

Carriage

Return/Enter

key.

The

modem

doesn't

count

spaces. It

counts

punctuation characters such

as parentheses

and

hyphens,

but ignores them.

The

following

command

instructs the

modem

to stop the

display

of

commands

(E0,

turn

off

the local

echo),

to dial

(DJ using

Touch-Tone

dialing (T),

and

to turn

off

the

speaker

(M0).

The

spaces

shown

are ignored by the

modem

and are only

included

here for readability.

AT

EO

DT

1234567

MO

er

If set to

X0

or

XI.

the

modem

defaults to pulse (rotary)

dialing.

To

have the

modem

use tone

dialing,

use the T

command,

which

also allows you to use the asterisk

(*

J and

Adaptive

Dialing

(X2-X7)

Pause(,)

COURIER HST

pound

sign(#).

The command may be included

in

the Dial

string, as

in

the above example, or issued separately:

ATT

<

er

The following command resets the modem to pulse dialing:

ATP

< e r >

You can switch from one dial type to another within a dial­ing sequence. For example, you might have a phone line
that only accepts pulse dialing (slower than Touch-Tone
dialing) but subscribe to a long-distance service that accepts
tone dialing. such as MCI. You can switch to tone dialing
once

you've

hooked into the long-distance service.

In

the

following example, a switch is made to tone dialing before
entering a service account number and the long-distance des­tination. (The commas are discussed shortly.)

ATDP

9,,7654321

,,T

55555,,13121234567

<

er

!\OTE

: The modem remain s set for Touch-Tone dialing until

it

is

reset or the

ATP

(pulse) command

is

reissued.

When any

of

the X2 through X7 options

is

in effect and

you

don't

issue a

di

aling type

in

the Dial string, the Courier

uses tone dialing. which

is

faster than the default pulse type.

However. if the phone company central office doesn

·1

have

Touch-Tone detection equipment. the modem can not

"break

dial'·

and continues to detect the dial tone.

If

this

occurs, the modem automatically reverts to pulse dialing.

A

comma

causes a two-second delay in the dial sequence.

The following example contains four-second delays at sev-

eral points:

ATOP

9,,7654321

,,T

55555

,,

13121234567

<

er

>

The first four-second pause

is

to access an outside line after

dialing 9. the second to make sure the remote computer is

ready for the user·s account number. and the third, to delay
before dialing the long-distance number.

Such pauses. however. may not be necessary. Experiment
and use delays only as required.

6-3

COURIER HST

Dial

and

Return

to

Command

Mode(;)

6-4

Use this option to have the modem Auto Dial a telephone

rather than a modem. The Courier dials, remains

off

hook

and returns the

OK

message, indicating it

is

in Command

Mode.
For example, if your phone

is

plugged into the modem you

can have the modem place a voice call. Issue the Dial com-

mand with a semicolon:

ATDT5551234;

<er>

When the modem returns the

OK

result, pick up your phone

receiver so you can talk to the other party and tell the

modem to hang up:

ATH

<er>

Similarly, you can call a recorded weather or other service.
Have the modem Dial. listen to the recording over the
modem's

speaker and, when

you're

finished, tell the modem

to hang up.
Another example is an information or other service that

requires a Touch-Tone entry

of

an ID as part

of

the log-on

procedures. The following sequence is an example.

ATDT1234567;

<er>

OK

ATDT65432;

<er>

OK

ATH

<er>

OK

(dial the service's telephone
number and return to Com­mand Mode)

(dial ID and return to Com­mand Mode)

(session

is

finished;

hang up)

Dialing

Letters

(")

Transferring

Calls

(!)

Wait

for

a

Second

Dial

Tone

(W)

COURIER HST

Quotation marks are used to have the modem dial abbrevia­tions and acronyms used as phone

"numbers,"

such as
DIAL USR (the USRobotics Sales Department's 800 num­ber). The option

is

called Quote Mode. Quotation marks

are inserted at the beginning

of

the alphabetic string:

ATDT"BBS-NEWS

<er>

If

you're including another command after the dial string,

use closing quotation marks before the additional command.
This command applies to modems

in

installations where

other modems share the phone line. The modem flashes the

switch-hook,

i.e.,

goes

off

hook 0.5 seconds, on hook for

0.5 seconds. and

off

hook again to dial the specified exten­sion. The following example includes instructions to return
to Command Mode (;) and to hang up (H).

ATDT ! 1234;

H

<er>

This command

is

useful in situations where you must wait
for a second dial tone before entering a password, for exam­ple, when using MCI, Sprint, or other long-distance service.
The following command tells the modem to dial the service
number, wait for the second dial tone, dial the ID, pause
two seconds. then place the long-distance call.

ATDT

5551234

W

12345,

3121234567

<er>

NOTE: This command executes only if result code option

X3

or greater has been issued.

If

the modem

is

set to

X2

or lower, the modem interprets the W as a comma (two-

second pause).

6-5

COURIER HST

Wait

for

an

Answer(@)

Reversing

Originate/Answer

Frequencies

(R)

6-6

CANCELING

DIALING

Some online services answer the phone and return a tape­recorded request for information before processing transac­tions.

In

such instances, the

(Zi

command can be used

in

the
Dial string to tell the modem to detect at least one ring, wait
for five seconds

of

silence at the other end

of

the call, and

then continue to execute the Dial string.
To use the

<!__i.

command, set the modem to X3, X4 or X7.

If the modem

is

set to X2 or lower, the modem returns

an

ERROR message when encountering the

(c_l

character

in

a command string.

If

set to XS or X6, the modem hangs

up

when it detects a voice answer and sends the VOICE

result code.
In

the next example, the modem

is

set to the X4 result code

option and dials a banking service. Each occurrence

of

(a.

in

the example indicates a five-second wait for silence after
taped requests from the bank for the labeled items. The
transaction code might be used, for example, to request
an account balance.

Password

/

ATX4

DT1234567

(u

12345

<u

6789

Ca

2

/ /

Account # Transaction Code

If

the necessary conditions

don't

occur-no

rings, or

no following five seconds

of

silence-the

modem times

out as

it

normally would (after 30 seconds).

It

then sends
the message NO ANSWER to the screen and aborts
the command.

This command allows calls to an originate-only modem. It
reverses the modem's originate/answer frequencies, forc­ing the Courier to dial out at the answer frequency. The
command follows the Dial command, before or after the

phone number:

AT

D1234567R

<er>

AT

DR

1234567

er>

To cancel dial-command execution, press

<any

key>.
If you inadvertently hit a key on the keyboard while the
modem

is

dialing, the call

is

canceled.

If

this occurs, type

the A/ command explained in the next section.

REDIALING

Reexeeute

the

Last

Command

(A/)

Automated

Redialing

(> ,

A>)

Continuous

Repeat(>)

Continuous

Reexecute

(A>)

Exiting

Repeat

Mode

COURIER HST

The most frequent reason for redialing

is

receipt

of

a busy
signal. The Courier HST provides three ways to redial.
as follows.

The

Al

command. which

doesn't

take the AT prefix or

a Carriage Return, redials one time:

A

When the modem receives a command, it stores the instruc­tion

in

its

command

buffer until the next AT command is

received. Note that

if

you've

sent the modem an additional
command since the Dial command, A/ reexecutes that com­mand instead

of

redialing.

These two commands, while they can be used to continu­ously repeat any command, are designed for automated
redialing. The first

(>)

is

included in the Dial command.

The second (A > )

is

used alone to redial the command

string in the buffer.

If

you know the modem you

're

calling

is

frequently busy.

include the Repeat command

in

the Dial string, as in either

of

the following examples:

AT

>

OT

1234567

<

er

>

AT

OT

1234567

> "

er

'>

The modem enters Repeat Mode, dials the number, waits
the default 30 seconds for a carrier, and hangs up. Then,
after a two-second pause,

it

redials.

The cycle continues until the modems connect or the modem
reaches a maximum

of

l

O

attempts. The

I

0-try limit

is

man-

dated by the Canadian Department

of

Communications
(DOC) to prevent tying up local telephone company
exchanges with unconnected calls.

This command combines the features

of

both the A/ and >

commands. The modem enters Repeat Mode as described

above, and continuously redials the Dial string in the com­mand buffer. Like the A/

command,

A> doesn't take the

AT prefix

or

a Carriage Return:

A >

Should you use > or

A>

with a command other than a Dial

string , abort the cycle by pressing

<any

key> .

To

abort automated redialing, be sure to press < any key>

when the result code appears, during the pause before the

6-7

COURIER HST

DIALING

A STORED

NUMBER

(DSn)

PULSE DIAL

MAKE

BREAK

RATIO (&Pn)

&PO

&P1

ESCAPE CODE

OPERATIONS

(+ +

+)

6-8

modem begins dialing again.

If

you press < any key> while

the modem

is

dialing, that dial attempt

is

canceled but the

cycle continues.
Chapter 5 includes instructions for storing up to four tele-

phone numbers in nonvolatile random access memory

(NRAM).

To

have the modem dial a stored number use the

DSn

command.

where

n

is

the

number's

position,

0-3.

in

NRAM.

In

the first

of

the next two examples. the phone

number

is

stored at position 0 , assumed by the modem if

there

is

no numeric parameter:

ATDS

·, er

ATDS3

<

er

If

you've

stored a long distance service number/access

code,

for

example

at position I , use the

DSn

command

to dial

the

number

and

code.

and follow that with a Dial

command

to dial the

call's

destination. (The spaces are included for

readability.)

AT

DS1 D

312

5556789

·

er

This

command

sets the ratio

of

the off-hook/on-hook (make/

break) interval when the modem pulse dials. The factory-set

default sets the modem for use

in

North America. The ratio

must be changed if the modem

is

used

in

the British Com-

monwealth, with the exception

of

Canada.

North America make/break ratio: 39%/

61

C/c.

This

is

the

default.

British

Commonwealth

make/break ratio : 33%/67%

(excluding Canada).
Once the modem

is

online to another system, the only com-

mand

it

recognizes

is

an escape code

of

three pluses, which

forces the modem back to

Command

Mode:

--

\V

a

il

(lfl

l'

,c

L·(1nd

:lltcr

cntcrin

~

th

e:

1:

ts

t

1t, ·

111

()f

data

--

T: r

c:

:

--

~-

---

\\

"a

it

O

TlL

'

,c

u 1

11d

he!(lrc:

typrn

~

:tll:

dat.1

Do not type the AT prefix

or

a Carriage Return. The guard

time

of

one

second before and after the code prevents the

modem from misinterpreting the occurrence

of

+ + +

in

the

transmitted data stream.

ARO

Mode

Response

Normal

Mode

Responses

WARNING

RETURNING

ONLINE

(0)

COURIER HST

If necessary. the character used

in

the escape code can be

changed by resetting S-register 2.

>-

See Appendix B-5.

If the modem has been connected under error control

it

automatically hangs up on detection

of

the escape code.

returns to

Command

Mode,

and sends the NO

CARRIER

result code.
In

Normal

Mode

, the modem returns to

Command

Mode

when it detects the escape code. However, it keeps the line
open

or

hangs up, depending on the setting

of

DIP

switch

9:

DIP

Switch

9

DOWN

UP

Response

to

+ + +

Modem

maintains
connection
OK

result code

Modem

goes on hook (hangs
up)
NO

CARRIER

result code

The factory-set position

of

DIP

switch

9

is

DOWN.

Retain

this setting if you want the modem to execute

commands

and return online. (See the O

command

.

below.)

Keep

in

mind, however. that this only applies to Normal

Mode

connections.

If you want an automatic disconnect when you issue

+ +

+,

set switch

9 UP.

An advantage

of

this

is

that

you're

not likely

to

inadvertently run up an all-night phone bill.

For unattended modem operations:

in

rare instances, the

modem may fail to recognize the

+ + +

escape code

sequence.

If

you are running the modem under software
control for unattended operations. we suggest you use the
surefire method

of

dropping the RS-232C DTR signal

for

at least

50

mifliseconds,

to ensure against costly phone

charges. Methods

of

turning the

DTR

signal off,

e.g

..

closing the communications port, differ from

one

com-

puter to another.

If

DIP

switch

9

is

DOWN

(on detection

of

the escape code
the modem maintains the connection), you can issue com­mands and then toggle the modem back online with the

0

command:

ATO

<-

er

>

6-9

COURIER HST

HANGING

UP

(Hn)

6-10

AUTOMATIC

ANSWERING

Suppressing

Auto

Answer

Points

to

Remember

If

DIP

switch 9 is UP for a Normal Mode connection and

for all

ARQ

connections, the modem automatically hangs up

when it detects the escape code.

If

DIP switch 9

is

DOWN,
first send the escape code to force the modem back to Com­mand Mode. When the modem sends the

OK

result code,

issue the command to hang up:

ATH

er

The Courier HST

is

shipped with DIP switch 5

DOWN.

Auto Answer suppressed.

To

set the modem to automati-

cally answer incoming calls, do one

of

the following:

I. Before powering on the modem, set DIP switch 5 UP.

When you

tum

the modem on,

it

answers incoming calls

on the first ring.

2.

If

the modem is on. use software control. The following
command instructs the modem to answer on the first ring.
(You can substitute a higher value. See the S-Register
summary in Appendix

8-5.)

ATSO

er

When

the modem senses a call coming in.

it

sends the result

code RING to your screen, goes

off

hook, and sends the

remote modem a high-pitched answer tone.

If

there

is

no
Carrier Detect within 30 seconds, the modem hangs up and
sends the NO

CARRIER

result code.

If

the connection

is

made, the modem sends a

CONNECT

result code. When the

call

is

disconnected by you

or

the remote user. the modem

hangs up and returns the NO

CARRIER

code.

To

disable Auto Answer, reverse steps I or 2 above. Set

DIP switch 5

DOWN

before powering on the modem or.

if

it

is

powered on, use the command to set the modem to

answer on zero nngs:

ATSO=O

er

1.

If

the modem

is

attached to a computer, you can set the

modem to receive calls when

you're

not there. Put the

modem in Terminal Mode and set

it

for Auto Answer.
Also set your software's file-save function to save incom­ing messages and/or files.

2. If

you've

attached your phone so

it

can be used for con-

ventional calls, disable Auto Answer when

you're

not

U.S.

CCITI

ANSWER

TONE

(

Bn

)

COURIER HST

expecting incoming calls. Otherwise. your modem may
answer the phone before you do. greeting your caller
with a high-pitched, irritating answer tone.

In

the United States and Canada. modems use a 2225 Hz
answer tone. Outside North America, most modems adhere
to the CCITT

V.

25

standard and send out a 2100 Hz lone

followed by a 2250 Hz tone. If

you're

expecting an overseas

call, set the Courier to use the

CCITT

answer tone. The

setting

won't

affect the

modem's

ability to connect with a

domestic modem although

it

will take slightly longer to con-

nect with a calling modem.

B@

CCITI

answer sequence, used to answer calls originating

outside North America.

81

U.S. answer sequence. This

is

the default.

6-11

USER INQUIRIES

(In)

COURIER HST

CHAPTER 7

QUERIES

AND

HELP

SCREENS

The Inquiry

comm

and has seve n opti ons. The mos t com-

monly used options display the follow

in

g inform a

ti

on:

A TI3 Call duration
A

TI4

Current settings

ATIS

NRAM

settings

ATI6 Link diagnostics summary

/(/)

The modem return s a 3-dig

it

product

co

de.

If

yo

u have a

problem and call USRobotic

s'

Techni

ca

l Support Depart -

ment, you may be asked for this product code.

I 1

The modem performs a checksum

of

it

s r

ea

d only

memor

y

(ROM) and returns the result to the scree n. This function is

us

ed

only in factory testing. The mod em should always read

th

e

same

number.

/2

The mod em performs a test

of

its random access me

mor

y

(RAM) and returns either

th

e

OK

(0) or

ERROR

(4) result

co

de , foll owed by

OK

when the test is completed. You may

want to use this co

mm

and as a checkpoint if the modem

appears to be malfunctioning.

/3

The modem returns the duration

of

th

e last call if set to K0.

It

displays the actual time if set

to

K 1. See the descripti on

of the

Kn

command

in

Chapter

5.

/4

The modem display s its curre

nt

configuration. Th e illustra-

ti

on on the followin g page is an

ex

ample.

7-1

COURIER HST

7-2

d t

i4

USRohotics Courier

HST

Settings

OK

c,1

[ , !

r,1

M,1

Q,0

v,1

x,1

B,!

BAUD,%00

PARITV,N

WORDL[N,8

DIAL,PULSE

ON

HOOK

TIMER

!At

!88

!G8

&H8

110

&M4

&N8

!P8

&Hl

!S8

!Vl

s00,001

S81, 888

S82 , 843

S03

013

S04

, 018

ses,0es

S86,

082

587,038

sea,

002 S89,B86

518,887 S 11,878

S

12,858

S13, 808 S14, 881

s1s,000

S16°888

S!?,888

S18°888

S

19,888

s20,

000

SZ!,888

s22,

817

szJ,

019

Figure

7.1-Sample

Result

of

ATl4 Command

/5

The modem displays the configuration stored

in

nonvolatile

random access memory (NRAM).

at

i 5

USRohotics

Courier

HST

NHAM

Settings.

Oi

DIAL,TONE

M,t

X,t

f,t

B,l

BAUD,%80

PARITV,N

WORDLEN,8

!Al

!Bl

H0

!HB

&10

!M4

!NB

!P8

&HZ

!S0

&YI

S02

843

S03

013 S84°010

S05,008

S86

001

S07

030 S08°001 S89°006

s10 001 s11 010

s1z,0se

s11,000

S19

000 SZI 000 S22°017

SZJ,019

STORED

PHONE

10.

1-312-982-5892

11:

12:

13:

Figure 7

.2-Sample

NRAM Settings Screen

(A

TIS)

/6

During a connection, the modem monitors and stores
information about link operations. When the call

is

ended,

you can request a diagnostic summary, as

in

the following

example.

S-REGISTER

QUERY (Sr?)

COURIER HST

Chu s sent

3669

Ch,1

rs

received

4249

Chars I os t 0
Datd

blocks

trans•itted

430

Ddtd

blocks

retransmitted

2

Line Revers a Is

OK

Figure

7.3-Sample

Link Diagnostics Screen (ATl6)

This

command

allows you to view the contents

of

a par­ticular S-Register. as in this example which requests
the contents

of

register

S0

("On

what ring will the

modem answer')'·

J:

ATSO?

er

Most registers store values that can be user-defined. How­ever. two registers that are not user-programmable can be
queried for the following diagnostic information.

S 7 7 The reason for a Link Disconnect when two modems try

to make an

ARQ

connection and fail.

or

when the remote

modem disconnects from an

ARQ

session. S

17

is

used for

debugging purposes. If

you're

having an ARQ-compatibility

problem and call USRobotics' Technical Support Depart-

ment. you may

be

asked to check S

17.

S20

The reason for a NO

CARRIER

result code when the

modem

is

in either

ARQ

or

Normal Mode. Reasons include

user aborts (pressing

<any

key>

during dialing). loss

of
carrier. and the automatic hangup that occurs when the
modem

is

set to &MS and calls a modem not operating

under error control.

7-3

COURIER HST

PHONE

NUMBER

QUERY (&Zn?)

HELP SCREENS

Stop

/

Restart

Display

Cancel

Display

Basic

Command

Set($)

7-4

At this

comma

nd .

th

e modem returns

th

e phone number

stored in NRAM at posi tion n, as in the

fo

ll

owing exam ple

that includes a sample modem response:

AT&Z3?

<

er

5551234

The

Co

urier

HST

provides four Help scree n

s:

summaries

of

th

e basic

AT

comma

nd set, extended ampersand

(&)

com-

mand set, S-reg ister func

ti

ons, and Dial com mand options.

The

fo

ll

owi ng co mmand stops

th

e display. Ho

ld

down the

Control key and type " S" :

"

Ctrl

·>

-S

To

restart the display. use the same

comma

nd

or

press

<a

ny key

>.

Either

of

the

fo

ll

ow

ing command s cance ls the display.

<

Ctrl

> -C

<...

Ctrl

>

-K

At AT$, the

Co

urier displa ys this

co

mmand set summar

y:

!$

HELP,

Ext

e11

ded

Co

Ml'ld

n

ds

!lt

11

: S

H

RRM

Se

ttings

An

swe r

c,

11

n=O

Link

Di

a

gnostics

Al

Rep

e

at

lti St

(0

111111

and

in

n=0

Ca

ll

Durd

ti

on

Mode

Bn

n:

0

CCI

TT

Ans w

er

Se

ljuence

n: 1

Reo

I

T

ir

tie

CI

eek

Mode

u· t

Be

11

An

s

wer

Sequence

Mn

n=B

Spe

aker

O

ff

Cn

n=

8

Tre1

ns•

it

ter

Off

n=1

Sped

ker

On

Until

CD

n: 1

Tr

11:

ns

rt

it

ter

On

tFZ

Spe

aker

A

IWdlJS

On

Dn

Dial

•

T

e!

epho

ne

Nu.her

n=3 Spe

itker

Off

During

Di,d

n=

B.

. 91•TPR, .

"

W~'

!

1-

Retur

n

On

- L

ine

DS

n

Di

iii

Sl

ord

Phc.i

ne

Hu

ber

Qn

n: 8

Resu

It

Codes

Sent

D$

HELP,

Di

a l

Co

,01

,rn

ds

li

=1

Qu

ie

t

(

Ho

Resu It

Codes)

E1

1

n=

0

Do

no

t

P.C

hO

Ch

us

Sr : n

Se t s

Reg is t e r

"

r

"

to

"

n

"

11

- l

ec

ho

CO

Hld

ll

d

C

hi!

r s

Sr?

Qu

er ~

Reg

is l e r

"

r

"

Fn

n: 8

H,

J

f

d

up

lex

S$

HEL

P,

S Reg i s

ter

s

n=l

Fu

l l

duple

x

Vn

n:

8

filu11er

ic

R

es

p

onses

Hn

nd

!t

On

Hook

( Hang

Ui

I

n

~

1

Ve

rb

a I R

esponses

n=l

Off

Hook

Xn

n:

8

B

as

ic

Resu

1

t Codes

In

ndl

Pr

oduct

Code

n: 1

E

xtended

Result

Co

d

es

n= t

C

hed

su

111

n

c2

-7

Adv

a

11

ced

Resu

It

Co

d

es

n:

Z

!A

M

Test

So

f

t wH e

Reset

n· J

Ca

I I

DurationJCJock

Re

pe

a t

Co1

1111

and

Str

ing

n· 1

Cu

r re

nt

Sett

ing s

HELP.

Co

11111

a

11d

S

u111111ar9

OK

Figure

7.4-Basic

Commands HELP Screen

Extended

Command

Set(&$)

S-Register

Functions

(S$)

COURIER HST

At AT&$. the Courier displays this summary

of

the amper-

sand command set:

AT!$

HELP,

Exteudtd

Co1111."111ds (CTRL-S

to

Stor,

CTRL

to

Cdnr:ell

&H11

n=0

Disable

IARQ

Re:.ult

Codes

&N11

n=0

Highest

Link

Speed

n-1

Al

!ow

sARQ

Result

Codes

n:1

J00

bps

n-]

2400

bps

&Bn

n:6

Vdr

idb

I e

DTE

Speed

0-2

1200

bps

"

6

%00

hp~

n1

Fixed

DTE

Speed

!Po

n:0

USA

Pulse

Dial

IF

Load

F

dCtory

Coufiguration

n:1

UK

Pt1lse

Didl

!Ho

n:6

Disdble

TX

da

L~

flow

control

&Rn

n-1

Ignore

RTS

"

1

CTS

n:2

RX

Data

t,

DTE ; RTS

high

n=Z

Xon

l Xof f

&Sn

n=6

DSR

d[wa9s

Oo

o- l

CTS

aol

X

on/Xof

f

0 1 Mode•

controls

DSR

!lo

11=0

Disable

RX

ddtd

flow

control

!W

Store

Current

Configuration

n-1

XontXof

f

!Yo

"

0

Destructive

Break

11-2

XonlXoff

Ch~

r S

filtered

n:1

Destruct

ive!Exped i ted

n-3

HP

Enq /

Ack

Ho

s t

Mode

ncZ

Nondestruct

ive/E,q.1ed i ted

0 4

HP

Enq!Ack

Tera

ind

I Node n=3

Nondestruct ive

/Unexp

ed i

ted

&H11

n=fl

Nor•~

l Mode

&Zn, s

Store

Phone

Nu•ber

"

4

AHQiNor•dl

Mode

&Zn?

Query

Phone

Nu11ber

n=S

ARQ

Mode

OK

Figure

7.5-Ampersand

Commands HELP Screen

At ATS$, the Courier displays a summary

of

the S-register

functions:

• ts$

HELP, S Register

Functions

CCTRL-S

to

Stop,

CTRL-C

to

C•ncell

S0

Ring

to

Anslifer

On

S1

Counts I of

Rings

S2

Escape

Code Char

S3

Carriage

Return

Char

S4

Line

Feed Char

SS

Backspace

Char

Sb

Wait

Ti•e/Dial

Tone

(sec)

S7

Wait

Ti•e/Carrier

(sec)

SB

Co••a

tnd

Jlepeat

Pause

(sec)

S9

Carrier

Detect

Ti•e

(1118sec)

S10

Carrier

Loss

Ti•e

(1110sec)

OK

S11

Touch Tone

Spacing

(Msec)

S

12

Escape

Code T

i•e ( 1158sec)

S!J

Bit

Mapped

S16

Test

Modes

S!7

LD

Reason

S19

Inactivit'J

Tiaeout

(ain)

S28

Disconnect

Reason

SZ!

Bre•k

Leog\h

SZZ

Xon

Char

SZJ

Xoff Char

Figure 7

.6-S-Register

HELP Screen

7-5

COURIER HST

Dialing

(D$)

7-6

At

ATD$,

the Courier displays this Dial

command

summary:

,

Id$

HHP,

Dial

Co

..

,nds

(CTRL-S lo

Stop,

CTRL-C

to

C,ocei

I

8- 9

Digits

to

Di

ct!

* I

Aux

I! i ary

Di

9

its

Tone

Oi,ding

OH

Pu I se

Did

Ii

119

Cal I an Ori

ginate

Only

Mode11

Pause

He•din

in

Co••dnd

Mode

Use('\

to

Di,d

Alpha Plione

l's

Wait

for

2nd

Dial

Tone (X3-X6)

Wait

for

an

Answer

(X3-X&)

Flash

Switch

Hoo~

Figure

7.7-Dial

Command HELP Screen

COURIER HST

TABLE

OF CONTENTS

PART

II. REFERENCE

APPENDIX

A-Error/Flow

Control Concepts A-I

Overview A- I

Throughput A- I

MNP Service Classes A- I
Error Detection/Retransmission A-2
Flow Control A-3

Example

1-

Transmit Data A-4

Example

2-Received

Data A-4

APPENDIX B- Summaries and Tables

B-1

The RS-232C Interface, with Pin Definitions B-1.1
Front End Indicators B-2.1

DIP Switch Summary B-3.1
Default Settings B-4. I

S-Register Summary B-5.1
ASCII Chart B-6.1

APPENDIX C- Alphabetical Command Summary C-1

APPENDIX

D-Problems

and Solutions

D-1

If You Still Have Problems D-3

APPENDIX

E-Additional

Operational Information

E-1

Using Both Voice and Data Communications E-1.1
High Speed/Low Speed Protocol E-2.1
Retrain Sequence E-3.1
PBX. Dedicated Line, and Leased Line Operations E-4.1
Hewlett Packard Installations E-5.1

APPENDIX

F-Technical

Specifications

F-1

GLOSSARY

G-1

INDEX

OVERVIEW

Throughput

MNP

Service

Classes

Service Class 1

Service Class 2

COURIER HST

APPENDIX A

ERROR/FLOW CONTROL CONCEPTS

At

9600 bps. the Courier HST uses the USR-HST error

control protocol, a proprietary protocol developed by

USRobotics. At 2400/1200 bps, the modem uses the MNP

error control protocol originally developed

by

Microcom.

Inc. and now

in

the public domain.

In

USRobotics imple­mentations, we use the general term ARQ (automatic repeat
request) to denote error control

at

all three speeds.

Error-free data transmission is ensured through two features:

• error-detection and retransmission techniques:

• data buffering and flow control.

NOTE: As with all protocols, error control only works when

the Courier HST connects with another modem that imple­ments the HST protocol at 9600 bps or the MNP protocol
at 2400/1200 bps.

Chapter 3 offers recommended modem settings to gain max­imum throughput at 9600 bps. Optimal throughput is about

1100 characters per second when the link speed

is

9600 bps
and the terminal transmits to the modem at 19.2k bps. The
design

of

the HST protocol builds on and enhances previous

protocols by integrating much

of

the additional error control

information (overhead) within the data blocks instead

of

transmitting separate ARQ data.
For optimal throughput at 2400/

! 200 bps under MNP, see

Service Class 3, below.
At

2400/ ! 200 the ARQ protocol implements one

of

three

MNP

service classes.

as

follows:

This service class, often called Block Mode, supports half­duplex (one way at a time) transmission. The sending
modem transmits a block

of

data and waits for an acknowl-

edgment from the receiving modem before sending the next.
Service Class 1

is

the slowest and is included because

some computer equipment

is

restricted to either sending or

receiving at any one time. This mode

of

operation is usually

observed

in

communications between terminals rather than

in

terminal-to-computer or computer-to-computer links.

This class, often called Stream Mode, supports full-duplex
transmission

in

which data flows in both directions at the

A-1

COURIER HST

Service Class 3

A-2

ERROR

DETECTION

RETRANS-

MISSION

same time. Throughput at Class 2, due to protocol over­head, achieves about 84%

of

the throughput

of

a normal
modem, or approximately 202 characters per second (cps)
at 2400 bps.

Service Class 3 incorporates Class 2 and is more efficient.
Modems sending at Service Class 3 strip the Start and Stop
bits from the data characters and transmit the data across the
link

in

bit format, as

in

synchronous transmission, rather

than

in

character format. The receiving modem reinserts the
Start and Stop bits for each character before passing the data
to the receiving computer or terminal.

This procedure offsets the protocol overhead loss so that
throughput

is

about 1089c that

of

a normal modem. Under

optimal conditions, two Class 3 modems operating at 2400

bps can exchange data at approximately 259 characters
per second.

When the modems negotiate their

MNP

connection, each

indicates its highest service level and they agree to operate

at the highest level possible, Service Class 3, 2, or

1.

The

Courier HST indicates Class 3

in

its

MNP

error-control
parameter. If necessary, the Courier automatically drops
back to meet the requirements

of

the other modem.

During an ARQ connection the transmitting modem divides

the data

it

receives from the computer or terminal into
blocks, and attaches header and trailer information. The
result

is

called a frame, as shown

in

Figure A. I.

....__H-EA_o_e_R_....__o_Ai:_A_._ . .

_\

..... \

..

DATA

I

TRAILER

Figure A

.1-

Transmission Frame

Included

in

the header or trailer are a frame number and
block-size information as well as a frame-check code. This
last code is derived by the sending modem through an algo­rithm performed on all

of

the data in the frame. The tech-

nique

is

called cyclic-redundancy checking (CRC).

The receiving modem performs the same computation and
checks to see if its results match the received CRC code.
If the results match, the receiving modem sends a positive
acknowledgement to the sending modem. Meanwhile, the

FLOW CONTROL

Flow

Control

Examples

COURIER HST

sending modem keeps a copy

of

a

ll

frames

it

sends until

each

is

positively acknowledged.

If

the CRC codes

don't

match, the receiving modem ini-

tiates the

automatic repeat request (ARQ)

procedure. The
receiving modem tells the sending modem which frame is
in

error, and

doesn't

accept any more frames until the frame

in

question

is

received correctly. The sending modem goes
back to the specified frame, retransmits it, and continues
from there.

In

this way the protoc ol protects against errors

and also ensures that the data arrives

in

seq uence.

When flow control

is

enabled , the modem stores data in a

buffer,

as shown in Figure A.2, and monitors how full the

the buffer is.

Transmit

Data

-

I

..__._.....

I

Data Link

-

ll:'i"":

Modem

Computer

/Terminal

Figure

A.2-Flow

Control Buffer

-

Received

Data

The buffer

is

used to store data transmitted to the modem

from the computer

or

terminal as well as data received over
the data link. Separate commands instruct the modem for
Transmit Data flow control

(&Hn)

and Received Data flow

control (&In,

&Rn).

Chapter 4 contains instructions on

when and how to use these commands.
The lab els used

in

the following examp les indicate the

following devices:
DTE

Data Terminal Equipment:

devices that are the source

or

final destination

of

transmitted data, such as a per-

sonal computer, mainframe, or terminal.

DCE

Data Communications Equipment:

also called Circuit-

Terminating Equipment, for our discussion indicates

the modems that establish and ot herwise control the
phone connection ( data link) .

A-3

COURIER HST

Example1-

Transmit Data

Example

2-

Received

Data

A-4

The

&Hn

command

allows you to select software flow con-

trol, hardware flow control,

or

both. Under software flow

control the modem sends the

DTE

the ASCII

XON/XOFF

characters described in Chapter 4. Under hardware control

the modem raises

or

lowers the

Clear

to Send (CTS) signal

via the RS-232C interface.

9600

bps

Data Link

Figure

A.3-Transmit

Flow Control

Assume that there are disturbances on the line (line hits) and
DCE2, the receiving

modem,

detects a transmitted frame

error.

DCE2

tells

DCE

I to retransmit the frame and accepts

no additional frames until

it

receives the affected frame

correctly.

Meanwhile , the

computer

/terminal

(DTE

I) continues send-

ing to

DCE

I. and data backs up

in

the buffer. As the buffer

approaches capacity.

DCE

I signals DTE I to stop sending

data.

DCE

I also retransmits the specified frame and con-

tinues transmitting. When enough data

is

transmitted to

half

empty

the buffer.

DCEI

signals

DTE!

to

resume

sending data.
As mentioned

in

Chapter

4,

Transmit Data flow control

is

also essential

if

the

DTE

is

set

to

send to the modem at a

rate higher than the link rate.

It

may be necessary

or

desirable to stop incoming data

temporarily, for example,

in

order to review what's on the

screen and take some kind

of

action.

In

the following dia­gram, the labels indicate operations when three different
command options are used, as follows:

&I I The user at

DTE

I sends an

XOFF

command

to the

modem to have

it

stop passing on the received data.

The

command

is also transmitted to the remote
modem. which stops sending. When the user wants
to receive more data, an XON

command

is

sent to

both modems to resume.

COURIER HST

&I2 The user sends the same XON/XOFF commands to

the modem. but the modem

doesn't

pass them on

to the remote modem. The reason is explained

in

Chapter 4.

&R2 If DTE! is a computer that supports the Request to

Send (RTS) signal at the RS-232C interface, RTS

is

lowered to signal the modem to stop passing on

received data.

&11

XON/

XOFF

Figure

A.4-Received

Data Flow Control

Be

sure to review Chapters 3 and 4 before using the error/

flow control commands.

A-5

CONTENTS

COURIER HST

APPENDIX B

SUMMARIES

AND

TABLES

B-1

The RS-232C Interface, with Pin Definitions
B-2 Front End Indicators
B-3 DIP Switch Summary
B-4 Default Settings
B-5 S-Register Summary
B-6 ASCII Chart

B-1

COURIER HST
APPENDIX

B-1

THE RS-232C INTERFACE, WITH PIN DEFINITIONS

DESCRIPTION

PIN

ASSIGNMENTS

B-1.1

The RS-232C interface (often referred to without the ··C

")

is

a standard developed by the Electronic Industries Associa­tion (EIA). It defines the signals and voltages used when
data

is

exchanged between a computer or terminal and a
modem or serial printer. Data is transmitted between the
devices via a cable with (typically) 25-pin connectors.

The entire standard covers many more functions than are
used in most data communications applications. The pin

assignments that are factory set

in

the Courier HST are

shown

in

the following table .

RS-232C INTERFACE PIN DEFINITIONS

Pin

Circuit

Function

Signal

Flow

2

BA Transmit Data Terminal

<-

Modem

3

BB Receive Data Terminal

---->

Modem

4

CA Request to Send Terminal

<-

Modem

5

CB Clear to Send Terminal

---->

Modem

6

cc

Data Set Ready

Terminal

---->

Modem

7

AB Signal Ground Terminal

.._..

Modem

8

CF

Carrier Detect Terminal

---->

Modem

12

SCF

Speed Indicate Terminal

---->

Modem

20

CD

Dat a Terminal Ready Terminal

<-

Modem

22

CE Ring Indicate Terminal

---->

Modem

NOTE:

Some

computer/terminal equipment supports only a

few

of

the RS-232C signal functions set in the Courier.

The

minimum requir ed

for

the modem to operate are Pins

2.

3,

and

7.

plus the Data Terminal Ready (DTR) override switch

ON (DIP switch I DOWN).

If

the DTR override

is

OFF,

Pin 20 is also required.

If

the modem is set for hardware

flow control

of

transmitted data

(&HI),

Pin 5 is required.

If

the modem

is

set for hardware flow control

of

received

data (&R2), Pin 4

is

required.

Symbol

HS

AA

CD

OH

RD

SD

TR

:VIR

RS

cs

ARQ

AL

Meaning

High Speed

Auto

Answer

/

Answer

Carrier Detect

Off

Hook

Received Data

Send Data

Terminal Ready

Modem

Ready/

Power

Request to

Send

Clear

to

Send

Error Control

Analog

Loopback

Status

COURIER HST

APPENDIX

B-2

FRONT END INDICATORS

ON

when the

Courier

HST

is

powered

on

or

com-

municating with

another

modem

at

9600

bps.

OFF

during data link negotiations at

2400

bps.

ON

when the

Courier

is

in

Auto

Answer

Mode and

when online with a calling

modem.

ON

when the

CD

override <DIP switch

6)

is

ON

(DOWN).

ON

if DIP switch

6

is

UP and the

Courier

receives a valid data signal (carrier) from a remote

modem.

indicating that data transmission

is

possible.

ON when the

Courier

takes control

of

the phone line

to establish a data link.
Flashes when a data bit is received by the

Courier

from the phone line.

or

when

the

modem

is

sending

result

codes

to the terminal or computer.

Flashes

when

a data bit is sent to the

Courier

by the

terminal

or

computer.

ON when the

DTR

override

(DIP

switch

I)

is ON

(DOWN).

ON

if

DIP

switch

I

is UP and the

modem
receives a Data Terminal Ready signal from the ter­minal

or

computer

via

RS-232C

Pin 20.

ON

when

the

Courier

is

powered

on.

ON

when

the

Courier

is

powered on

if

your

computer

supports RTS (Pin 4) on the RS-232C interface.*
ON

until the

modem

lowers

CTS

(Pin

5)

on

the

RS-232C interface when

Tran

smit Data hardware flow

control is enabled.

Automatic Repeat Request.

ON

when the

Courier

is

set to

&M4

or &MS and successfully connects with

another

modem

under

error

control.

ON

when the

modem

is

in

Analog Loopback Self-Test

Mode.

*

If

RTS

is

supported and the

Courier

is

set to

&R2

for Received Data hardware flow control.

the

RS

indicator goes

OFF

when the

computer

lowers RTS.

B-2.1

COURIER HST

APPENDIX

B-3

DIP SWITCH

SUMMARY

PURPOSE

OPERATIONS

The Courier 's DIP switches, located at the rear

of

the
modem, are for adapting the modem to your equipment
and personal requirements. You may also want to experi­ment and review your computer or terminal documentation
as necessary.

Some users are able to move a single switch with a finger
tip. If this

doesn't

work for you, use a toothpick

or

other

small instrument.
The DIP switch settings are power-on defaults, read by the

Courier when it is turned on.

If

changed when the modem

is on, switches

2-5

and

9

require the A TZ (software reset)
command to initiate the new settings. The remaining (hard­ware) switches are automatically operative when set UP

or

DOWN

.

DIP SWITCHES: UP

=

OFF (OPEN), DOWN ON (CLOSED)

Factory

Switch

Setting

DOWN

2

UP

3

DOWN

4

UP

5 DOWN

6 DOWN

8-3.1

Function

Data Terminal Ready Override

UP DTR normal; RS-232C Pin 20 controls modem

DOWN

DTR always ON (override)

Verbal/Numeric Result Codes
UP Verbal (word) messages
DOWN Numeric codes

Result Code Display
UP Quiet Mode, no display
DOWN Result codes displayed

Command Mode Local Echo
UP Keyboard commands displayed
DOWN Display

of

commands suppressed

Auto Answer
UP Modem answers on first ring
DOWN Auto Answer suppressed

Carrier Detect Override
UP RS-232C Pin 8 indicates when modem

is

online

and a carrier data signal is present

DOWN Carrier Detect signal always ON (override)

Switch Setting

7 UP

8

DOWN

9

DOWN

10

UP

Quad

UP

Switch

COURIER HST

Function

Single/Multiple Phone Installation

UP Single phone line connection (RJ

11

jack)

DOWN

Multiple phone installations (RJ

12

or

RJ

13

jack);

when the modem goes

off

hook the A/ A I leads on

the

RJ

12

or

RJ

13

connector are shorted and the
extension light goes on, indicating that the line
is busy

Command

Set Recognition

UP

Command

set recognition disabled (Dumb Mode)

DOWN

Normal operations (Smart Mode)

Normal Mode Escape Code

(+++)Operations

UP

When

escape code is sent, modem hangs up,

returns to Command Mode, displays NO

CARRIER

DOWN

When

escape code is sent, modem retains connec-

tion, returns to Command Mode, displays

OK

NOTE: Under error control, modem always hangs up

at + +

+.

Power-on Software Defaults

UP Load from

NRAM

DOWN

Load factory settings from

ROM

RS-232C Modem/Terminal Interface

UP

Normal assignments: Pin

2-terminal

to modem;

Pin

3-modem

to terminal

DOWN

Alternate assignments: Pin

2-modem

to terminal;

Pin

3-terminal

to modem

The need to change this setting

is

rare. Carefully review

your computer or terminal documentation before turning

this switch ON.

8-3.2

COURIER HST

APPENDIX B-4

DEFAULT SETTINGS

USER-

PROGRAM-

MABLE

DEFAULTS

NRAM Options

You can create your own default configuration and store

it
in nonvolatile random access memory (NRAM) using the
& W

command

described in Chapter 5. Your defaults are
then loaded into random access memory (RAM) as long
as DIP switch

IO

is

UP when you power on the modem.

To

view your NRAM settings at any time, use the A TIS

command.

The following tables list the options stored in NRAM.

If

DIP switch

IO

is

DOWN

at power on, the factory settings

listed in the table are loaded instead. The first time the

modem

is

turned on, the

NRAM

settings are the same as

the factory settings.

Factory Setting

Normal/error control modes &M4 Normal/ARQ
Display

of

error-control response codes

&Al

Enabled

Transmit data flow control

&H0

Disabled
Received data software flow control &I0 Disabled
Received data hardware flow control

&RI

Ignore RTS

Terminal-to-modem speed

&B0

Follow connection rate
Link speed (modem to modem)

&N0

Variable link operations
Data Set Ready (DSR) signal

&S0

Override
Stored telephone number

&Z0-3=0

Blank

Tone/Pulse dialing

p

Pulse dial
Online local echo

Fl

Echo

OFF

Speaker control

Ml

ON

during dial through

connect
Result code sets

XI

Extended
Pulse dial make/break ratio

&P0

N. American
U. S ./CC ITT answer tone

B0

N. American

Break handling

&YI

Clear buffer, send

Break immediately

Parity setting detected from AT command

-

Even parity

B-4.1

COURIER HST

NRAM $-Register Options Factory Setting

Escape code character, ASCII

S2=43

Carriage Return character, ASCII decimal

S3=

13

Line Feed character, ASCII decimal

S4=

10

Backspace character, ASCII decimal

SS=

8

Dial wait-time, sec.

S6=

2

Carrier wait-time, sec.

S7=30

Dial pause /reexe cute tim

e,

sec.

S8=

2

Carrier Detect time, I

/I

0th sec.

S9=

6

Carrier loss wait-time, I/10 th sec.

SlO=

7

Touch-Tone duration, spac ing, msec.

SI I

=70

Escape code guard time, 1

150

th sec.

Sl2

= 50

Bit-mapped functions, S-Register

13

Sl3=

0

Inactivity/hang up timer , S-register

19

S19=

0

Received break length, 10-msec. units

S21

=

10

XON

character, ASCII S22 =

17

XOFF

character, ASCII S23 =

19

8-4.2

COURIER HST

APPENDIX

B-5

S-REGISTER

SUMMARY

Register

S0

SI

S2

S3

S4
S5

S6

S7

S8

B-5.1

USAGE

The default values are those user s typi

ca

lly require. Change

the settin gs with the

ATSr

=

n

comm

and, where

r

is the reg-

ister and

n

is a decimal value from

0-

255 :

ATS13

= 8

<

er

>

The modem does not perform a value-range check . A value
yo u select may not wo rk with s

om

e equipme

nt

, and you '

ll

have to r

ea

djust

th

e setting.

To display

th

e co

nt

ents of a r

eg

ister, use AT

Sr?

as in this

example:

ATS20?

<<

Cr >

Default Function

See DIP Sets th e

numb

er of rings on which to answer when

in

Auto

Switch 5 Answer Mode. Default

=

1, equivale

nt

of

DIP switch 5

UP

. S0

=

0 or DIP switch 5

DOW

N (factory setting) sup-

presses Auto Answe

r.

0 Counts and stores the number of rings from an

in

co

m-

in

g ca ll.

43

13

10

8

2

30

2

Stores the

ASC

JI

decimal code for

th

e escape cod e charac-

ter. Defa ult character

is

..

+

".

A valu e

of

128

-255

disables

the esca pe code.

Stores th e ASC

II

decimal code for the

Ca

rriage Return

characte

r.

Stores the

ASC

JI

decimal code fo r the Line Feed characte

r.

Stores the ASC

II

dec imal

co

de fo r the Bac kspace character.

A va

lu

e

of

128- 255

di

sables

th

e Backspace k

ey's

delete

func

ti

on.

Sets

th

e numb er

of

seconds the modem wa

it

s before dialing.

If

set to X2. X4.

X6.

or

X7.

the modem ignores this regis-

ter and dials as soon as

it

detects a

di

al tone (fa st dials).

Sets

th

e number

of

seconds th e modem wa

it

s

fo

r a

ca

rrier.

May be set

fo

r much long

er

durati on i

f.

for

exa

mpl

e,

the

modem is o

ri

ginating an international

co

nn

ec

ti

on.

Sets

th

e du ra

ti

on. in seconds, for

th

e pause (.) option

in

th

e Dial

co

mm and and the pause between command

re

exec utions ( > and A> commands).

Register

S9

SIO

S

II

Sl2

Sl3

S14
S15
S16

Default

6

7

70

50

0

COURIER HST

Function

Sets the

required

duration,

in tenths

of a second,

of

the

remote

modem's

carrier

signal

before

recognition

by

the

Courier

(Carrier

Detect

Time).

Sets the

duration.

in tenths

of a second,

that the

modem

waits

after

loss

of

carrier

before

hanging

up.

Sets the

duration

and

spacing,

in

milliseconds,

of

dialed

Touch-Tones.
Sets the

duration,

in fiftieths

of a second,

of

the

guard

time

for the

escape

code

sequence.

Bit-mapped

register.

Select

the bit(s)

you

want

on,

and set

Sl3

to the total

of

the

values

in

the

"Value"

column.

For

example.

ATS13=20

enables

bits 2

(value=

4)

and

4

(value

= 16).

Bit

Value

Result

0 I

Reserved

2

3

4

5
6

7

Reserved.

Reserved.

2

4

8

16

32

64

128

Reverse

normal

Auto

Answer

operation:

on

incoming

RING,

enter

Originate

Mode

and

look for

Answer

tone

Disable

250

msec.

pause

before result

code
display
When

DTR

goes

from low to

high.

Auto

Dial the

number

stored in NRAM at

position

0

At

power

on

or

reset.

Auto

Dial the

num-

ber

stored

in NRAM at position 0

Reserved

Disable MNP Service

Class

3 (used for

testing

Service

Class

2)

Watchdog

hardware

reset,

same

as

power

on

(used

in factory testing)

:-.1odem self-test.

See

Chapter

2 for test

procedures.

0 Data

Mode

( no testing)

Analog

Loopback

2 Dial

Test

4

Test

Pattern

5

Analog

Loopback

with

Test

Pattern

B-5.2

COURIER HST

Register Default

Function

Sl7

0

Stores the reason for a received ARQ Link Disconnect. May

be requested by Technical Support

if

you're

having a prob­lem connecting in ARQ mode with another ARQ-mode
modem. At A

TS]

7')

the modem returns one

of

the following

codes:

I

Received data unit other than link request

2

Incompatible protocol level

3

Unknown parameters

in

link request

4

Remote modem retry timeout (Max.

12

tries)

5

Inactivity timeout

6

Destination user not found

254

Peer protocol error

255

User-initiated disconnect

SIS

Reserved.

Sl9

0

Sets the duration, in minutes, for the Inactivity Timer. The
timer

is

activated when there is no activity on the phone

line. At the timeout the Courier hangs up.

S20

0

Stores the reason for the NO CARRIER result code. At
A TS20? the modem returns one

of

the following codes:

0

Key press abort

I

DTR dropped

2

Escape code (

+ +

+)

issued

3

Loss

of

Carrier
4 Inactivity timeout
5

Automatic hangup with ARQ incompatibility
(&MS Mode)

6

ARQ Retry timeout (Max.

12

tries)

7

ARQ Received Link Disconnect (See S

17)

S21

10

Sets,

in

I 0-millisecond units, the length

of

Breaks sent

from the modem to the local terminal.

S22

17

Stores the ASCII decimal code for the XON character.

S23

19

Stores the ASCII decimal code for the XOFF character.

B-5.3

ASCII

CHART

DEC

HEX

CHAR

DEC

HEX

CHAR

DEC

00

00

NUL

32

20

SP 64

01

01

SOH

33

21

!

65

02

02

STX

34

22

..

66

03 03

ETX

35

23

#

67

04 04

EOT

36 24

$

68

05 05

ENO

37

25

O/o

69

06

06

ACK

38 26

&

70

07

07

BEL

39

27

'

71

08 08

BS

40

28

(

72

09 09

HT

41

29

)

73

10

OA

LF

42

2A

*

74

11

OB

VT

43

28

+

75

12

oc

FF

44

2C

'

76

13

OD

CR

45

2D

-

77

14

OE

so

46

2E

78

15

OF

SI

47

2F

I

79

16 10

DLE

48

30

0

80

17

11

XON

49

31

1

81

18

12

DC2

50

32

2

82

19 13

XOFF

51

33 3 83

20

14

DC4

52

34

4 84

21

15

NAK

53

35 5 85

22

16

SYN

54

36 6 86

23

17

ETB

55

37

7

87

24

18

CAN

56

38

8 88

25

19

EM

57

39

9 89

26

1A

SUB

58

3A

90

27

18

ESC

59

38

'

91

28

1C

FS

60

3C

<

92

29

10

GS

61

30

=

93

30

1E

RS

62

3E

>

94

31

1F

us

63

3F

?

95

HEX

CHAR

40

@

41

A

42

B

43

C

44

D

45

E
46 F
47

G
48

H
49 I
4A

J

48

K

4C

L
4D

M

4E

N

4F

0

50

p

51

Q

52

R

53

s

54

T

55

u

56 V
57

w

58

X

59

y

5A

z

58

[

5C
5D

J

5E

'

5F

-

COURIER HST

APPENDIX B-6

ASCII CHART

DEC

HEX

CHAR

96

60

'

97

61

a

98

62

b

99

63

C

100 64

d

101

65

e

102

66

f

103

67

g

104

68

h

105

69

i

106

6A

j

107

68

k

108

6C

I

109

6D

m

110

6E

n

111

6F

0

112

70

p

113

71

q

114

72

r

115

73

s

116

74

t

117

75

u

118

76

V

119

77

w

120

78

X

121

79

y

122

7A

z

123

78

{

124

7C

I

125

70

}

126

7E

-

127

7F

DEL

B-6.1

Requirements

Command/

Options

&

A

Al

A>

<Any

key>

AT

8n

80

81

COURIER

HST

APPENDIX

C

ALPHABETICAL

COMMAND

SUMMARY

Additional command summaries are on the bottom panel
of

the modem and

in

the Quick-Reference Card.

I. Type commands

in

either upper or lower case.

2.

All commands except A/,

A>

and + + + are preced-

ed by the AT prefix and are executed with the Enter/
Carriage Return key

(<er>).

3. Command length = 40 characters maximum. The

modem

doesn't

count the AT prefix, Carriage Return

character,

or

spaces.

It

counts but

doesn't

act on punctua-

tion such as hyphens and parentheses.

4. A missing numeric parameter

is

assumed to be zero, as

in

the command to hang up: A TH

<er>

is

the equivalent

of

ATH0

<er>.

BASIC

COMMAND

SET

Function

See the Extended Command Summary that follows this
Basic Set.

Force Answer Mode when the modem hasn't received

an

incoming call.
Reexecute the last issued command one time. A/ doesn't

take the AT prefix

or

a Carriage Return.

Reexecute the last issued command continuously until can­celed by pressing

<any

key>.

Dial strings are reexecuted

ten times after which execution terminates.

A>

doesn't take

the AT prefix or a Carriage Return.
Terminate current dialing operation resulting from an issued

Dial command; terminate Repeat mode ( > or

A>).

Attention: lets the modem know commands are being issued
to it.

Must

precede all other commands except A/,

A>

and + + +.

U. S ./CC ITT answer sequence.
CCITT (overseas) answer sequence.

U.S. answer sequence (Default).

C-1

COURIER HST

Cn

D

C0

C1

p

T

w

(a

R

Transmitter enabled/disabled.
Transmitter disabled; receive-only condition.
Transmitter enabled (Default).
Dial the number that follows and enter Originate Mode.

Optional parameters:

Pulse dial (Default).
Touch-Tone dial.
(Comma) Pause for 2 seconds.
Return to Command Mode after dialing.
Dial the letters that follow.

Transfer call (flash switch-hook).

Wait for second dial tone (with

X3

or higher).

Wait for an answer (with

X3

or higher).

Reverse frequencies.

DSn

Dial the phone number stored in NRAM at position n

(n

=

0-3).

En

Fn

Hn

C-2

E0

E1

Command Mode local echo (display)

of

keyboard commands

ON/OFF. (DIP switch 4

is

factory set

to

Command Mode

echo

ON.)
Local echo OFF.
Local echo ON.
Online local echo

of

transmitted data ON/OFF. Sometimes

referred to as the Duplex setting.

F0 Local echo ON. Sometimes called Half Duplex. Modem

sends a copy to your screen

of

data it sends to the re-

mote system.

F1

Local echo

OFF

(Default). Sometimes called Full

Duplex. Receiving system may send a remote echo

of

data

it

receives.

H0
H1

On/off hook control.
Hang up (go on hook).
Go

off

hook.

In

10

11

12
13
14
15
16

Kn

K0

K1

Mn

M0

M1
M2
M3

0

p

On

00
01

Sr

=n

Sr?

T

COURIER

HST

Inquiry.
Di

s

pl

ay produ ct code.

Display results

of

RO M chec ksum .

Display re sults

of

RAM test.

Dis

pl

ay ca

ll

dura

ti

on or rea l time (see

Kn

).

Displ ay current modem settings.
Dis

pl

ay NRAM se ttings.

Display Link diagnostics.

Modem

cl

ock operation: Call-duration or Re

al

-time Mode.

Return ca

ll

dura

ti

on at ATl3 (Default

).

Return actual time at ATI3. Clock is set using

ATI3 = HH:MM:SS

Kl.

Monitor (speaker) control.

Speaker always OFF.
Speake r ON until carrier is established (Default).
Speaker always ON.
Speaker ON a

ft

er last digit dialed and until

ca

rrier is

established.
Return online after c

omm

and execution.

Pulse dial (De

fa

ult

).

Quiet Mode: result codes di splayed/suppressed. (DIP swit ch
3 is factory set to

di

s

pl

ay result

co

des.)

Result codes dis

pl

ayed.

Re sult

co

des suppressed

("

quiet

")

.

S-register

comm

ands:

r

is a

ny

S-re gister;

n

mu st be a dec

i-

mal number betw een 0 and 255.

Query r

eg

ister

r.

Tone dia

l.

C-3

COURIER

HST

Vn

Xn

C-4

V0

V1

Return result codes in words

or

numbers (Verbal/Numeric

Mode). (DIP switch 2

is

factory set to verbal result codes.)
Numeric Mode.
Verbal Mode.
Result code set options. Use the following table

(Default

=

XI.

Extended set, codes

0-5.

IO

and 13).

RESULT CODES OPTIONS TABLE

Commands

XO

X1

X2 X3

X4

X5 X6 X7

Result

codes

0/0K

X

X

X

X

X

X

X

X

1/CONNECT X X X

X

X

X

X X

2/RING X X X X X

X

X X

3/NO CARRIER

X X X X X X X X

4/ERROR X

X X X X X

X

X

5/CONNECT 1200

X

X

X

X

X

X

X

6/NO DIAL TONE X X X

X

7/BUSY

X

X

X

X X

8/NO ANSWER

X X X X X

9/Reserved

10/CONNECT 2400

X X

X

X

X

X

X

11/RINGING

X

X

X

12/VOlCE

X

X

13/CONNECT 9600 X X X X X X X

Functions

Adaptive

Dialing X

X X X X X

Wait

for

2nd

Dial

Tone

(W)

X

X

X

X

X

Wait

for

Answer

((cl)

X

X

X

X

X

Fast Dial X

X X X

MHE:

Depending on the &A setting. the following result

codes are enabled/disabled. The default

is

&A

1,

/ ARQ

codes enabled.

15

CONNECT

12001

ARQ

16

CONNECT 2400/ ARQ

17

CONNECT 9600/ ARQ

z

+++

>

$

&$

0$
S$

< Ctrl>

-S

< Ctrl> -C

or

< Ctrl>

-K

COURIER HST

Reset the modem to its NRAM settings; initiate new settings
of

DIP switches

2-5

and

9.

Escape code, preceded and followed by a guard time

of

at least one second

of

no data transmission. The modem

responds to

+ + +

by returning to Command Mode and

doing the following:
ARQ

Connection-Hangs

up

Sends NO CARRIER result code

Normal

Connection-

DIP Switch 9 DOWN (ON, Factory setting):

Retains phone line connection

Sends OK result code

DIP Switch

9

UP (OFF):

Hangs up

Sends NO CARRIER result code

Repeat the command continuously until canceled

by

pressing

< any

key>.

If

used in a Dial string, automated redialing

terminates after ten attempts.
Help command summary request.
Help extended command summary request.
Help Dial command summary request.
Help S-register summary request.
Stop/restart display

of

Help screens.

Cancel display

of

Help screens.

C-5

COURIER HST

Command/

Options

&An

&A0
&A1

&8n

&80
&81

&F

&Hn

&H0
&H1
&H2
&H3

&In

&10
&11
&12
&13
&14

&Mn

&M0
&M1
&M2
&M3

&M4

&M5

C-6

EXTENDED COMMAND SET

Function

En

able/disable /ARQ result codes.
Suppress /ARQ result codes.
D

is

pl

ay /ARQ result codes (Defa ult

).

Data Rate, terminal-to-modem (DTE/DCE) va

ri

a

bl

e or

fix

ed.

DTE/DCE rat e

fo

ll

ows conne c

ti

on

ra

te

(De

fa

ult).

DTE/DCE

fi

xed at

th

e DTE setting. A

ll

owa

bl

e

ra

tes are

1

9.2

k, 9600, 2400, 1200, 300 bp s.

Load factory

(R

OM) settings into random access memory

(RA

M)

.

Transmit Data

fl

ow control.

Fl

ow control

di

sabled (Default).

Hardware (CTS, P

in

5) flow control.

Sof

twa

re

(XON!XOFF)

fl

ow co

nt

ro

l.

Ha

rd

wa

re

and software co ntrol.

Rece

iv

ed Data software flow contro

l.

Fl

ow co ntrol di sa

bl

ed (Default).

XON/X

OFF

to local modem and remote system.

XO

N/

XOFF

to local modem o

nl

y.

Host Mode, Hewlett Packard p

ro

tocol.

Terminal Mod e, Hewlett Packa

rd

protocol.

Normal

or

Error Control Modes.
Normal Mode.
Reser

ve

d.
Reserved.
Reserved.
No

rm

al/ ARQ Mode

-Normal

if ARQ connec

ti

on ca nnot be

made (Default

).

ARQ Mode- hang up if ARQ connection ca

nn

ot be made.

COURIER HST

&Nn

Link Data Rate (DCE/DCE) variable or fixed. With fixed

link rate, modem hangs up if called or calling modem

is

operating at a different rate.

&N0

&N1
&N2
&N3
&N4
&N5
&N6

&Pn

&P0
&P1

&Rn

&R0

&R1
&R2

&Sn

&S0

&S1

&W

&Yn

&Y0

&Y1

&Y2

&Y3

Normal link operations; negotiate highest possible link rate
with remote modem (Default).

300 bps .

1200 bps.
2400 bps.
Reserved.
Reserved.
9600 bps.
Pulse dialing make/break ratio.

Use North American make/break ratio (Default).
Use British Commonwealth make/break ratio (excluding

Canada) .
Received Data hardware flow control (RTS , Pin 4).
Reserved.

Ignore RTS (Default).
Received data output to terminal on RTS high; used only

if terminal supports RTS (Pin 4).

Data Set Ready (DSR, Pin 6) override.

DSR override. always ON (Default).

Modem controls DSR.

Write current settings to nonvolatile random access memory

(NRAM).

Break handling. Destructive Breaks clear the buffer; expe-

dited Breaks are sent immediately to the remote system.

Destructive.

don't

send Break.
Destructive, expedited (Default).
Nondestructive, expedited.
Nondestructive, unexpedited; modem sends Break

in

sequence with data received from terminal equipment.

C-7

COURIER HST

&Zn=s

&Zn?

C-8

Write the following Dial string (s) to NRAM at position n

(n

=

0-3).

Maximum length

of s is

36 characters.

Display the phone number stored in NRAM at position

n.

PROBLEM

COURIER HST

APPENDIX D

PROBLEMS AND SOLUTIONS

You may occasionally encounter one

of

the problems listed
here. They are divided into two categories: before and dur­ing the exchange

of

user information over the data link.

SUGGESTED SOLUTION

Before

Establishment

of

the

Data Link

Yo

ur

modem

.

..

Doesn't

answer

the

phone

or

go

"off

hook"

to

dial

a

number

Doesn't

respond

OK

when

you

type

AT

< er>

Check to make sure your computer or terminal

is

providing

a positive voltage on pin 20 (Data Terminal Ready)

of

the

RS-232C connector.

>

See Appendix

8-3.

DIP switch I.

1.

Make sure

you're

typing

in

either upper case or lower
case letters. not a combination, and that you type a
Carriage Return.

2. If you 're using a computer, make sure

it

is

in

Terminal

Mode .

3. Check to see that your terminal or software

is

set to the

correct bit rate and word length

(7

bits with

or

without

a parity bit,

or

8 bits and no parity).

If

you're

using a
computer, make sure your software is set to the correct
communications port.

4. Check that DIP switch 3 is DOWN, for result code
display. and that DIP switch 2

is

UP, for verbal result

codes.

If

not, change the switch(es) and issue ATZ

< er > .

Or

issue whichever

of

these commands

is

needed:

ATOO ,

er

ATV1

, er

(to display the message)
(to display a verbal message)

5. Your machine may require the Carrier Detect override

(DIP Switch 6 DOWN), but

you've

changed the factory

setting. Check Appendix B-3.

6. A rare condition is that your terminal/computer reverses

the send/receive functions

of

RS-232C pins 2 and 3.

>

See Appendix

B-1

, Appendix

8-3,

Quad switch,

and your equipment documentation.

D-1

COURIER HST

PROBLEM SUGGESTED SOLUTION
Before

Establishment

of

the

Data Link

Your

computer

...

Reacts

as

though

a data

link

has been

established,

but

no

call has been

received

When

the

modem

is in

Answer

Mode,

acts

as

if

a

Carriage Return

has been

entered,

but

nothing

has been

typed m the

keyboard

Both

modems

...

Exchange

carrier

signals,

but

fail

to

establish a

communications

link

D-2

DIP Switch 6

is

set

DOWN

at the factory for Carrier Detect
override, but your system may be reacting to improper sig­nals received on pin 8

of

the RS-232C connector. Set DIP

switch 6 UP (OFF).

Your software may be misreading signals from the modem

as

it

automatically sends a Carriage Return and a Line

Feed before and after the

RING

and

CONNECT

messages.

Entering the Quiet Mode

command,

A TQ 1

<er>.

should

solve the problem.

1.

Check to make sure the proper bit rate, word length.

parity and number

of

Stop bits have been selected.

2.

If

that

doesn't

correct the problem.

it's

likely that the

quality

of

the phone connection

is

poor and that the

other modem is missing the signals your modem

is

transmitting. The variable quality

of

phone line connec-

tions may be due to any number

of

conditions in the

phone service's equipment or the current environment.

Try several calls, and if you still

can't

get through, try

calling another modem.

If the second modem accepts

your call. the problem lies with the modem you first
tried to call.

3. Make sure the modem at the other end

of

the line

is
USR-HST compatible at 9600 bps. Y.22bis-compatible
at 2400 bps. Bell

2 l 2A-compatible at 1200 bps, or Bell

103-compatible at 300 bps. These are the common sig­naling standards for full duplex dial-up network trans­mission

in

the U.S.

PROBLEM

During Data Transfer

Your screen

displays

...

Only brackets

Random (gar-

bage) characters

Double

characters

IF

YOU

STI

LL

HAVE

PROBLEMS

COURIER HST

SUGGESTED SOLUTION

Check to make sure both modems are

at

the same bit rate,

word length, parity and number

of

Stop bits.

If

the settings

are correct, the problem may

be

with the phone line. Try

the following measures:

1.

Try placing the call again. The phone company routes
even local calls differently each time you call.

2. Try calling a different modem to see if the problem per­sists. (However, if it does, the problem may still be with
the phone line.)

3.

If

you are using a long-distance service and the problem

persists, you might try using a different service.

Make sure both modems are set

at

the same bit rate, word

length, parity, and number

of

Stop bits .

The modem's online local echo

is

probably

ON

. If the

modem's

in

Normal Mode, return it to Command Mode

(use

+ +

+)

when

it's

convenient, and then type:

ATF1 < er>

If

the modem's

in

an ARQ connection the only alternatives

are to put up with the problem until you disconnect or to

hang up ( type

+ + + ) ,

issue the A

TF

I command, and

call again.

The problems described above are

by

far the most common

ones that users encounter.

If

the suggestions

we've

given

don't

clear up your difficulties, try the following:

1.

Review the manual carefully to see if you've missed

something.

2. Call

or

visit your dealer. Chances are your dealer will

be

able to give you the assistance you need . This

is

much
more efficient and time-saving than returning the modem
to USRobotics.

D-3

COURIER HST

D-4

3.

If

your dealer ca

n't

clear up your difficulties, call

the USRobotics Technical

Supp

ort Department at

800

/982-5151 (

in

Illinois, 312 /982-5151).

Our

Service
Representativ es will be happy to give you assistance
ove r the phone Monday throu gh Friday from 8:30

a.m.

to 5 p.m. (Central

Time

Zone).

4.

If

necessary,

th

e Service Representative you

ta

lk

to
may give you a Return Materials Authorization (RMA)
number.

Mod

ems without an RMA number will not

be accepted.

5.

If

you do return the modem to us , please follow this

procedure­a. Ship the unit. postage paid, in its original container.

If

the origin al container is not available. pack the modem
carefully

in

a strong box

of

co

rrugated cardboard with

plenty

of

packing materia

l.

b. Be sure to include your RM A number

in

side the pack-

age, along with your name and address.

Put your

return address and your

RM

A number

0

11

th

e shipping

label as

11

·ell.

c. Ship the well-packed mod

em

to the following address.

Technical Support Department

USRobot ics. Inc.

8 I

00

North McCormick Boulevard

Sk

ok ie. Illinois 60076

d. Please note that USRobotics will not accept package s

sent

COD.

so be sure to send the modem postage

paid.

e. US Robo

ti

cs w

ill

repair yo ur modem and return

it

to

you via Un

it

ed Parcel Service.

CONTENTS

COURIER HST

APPENDIX E

ADDITIONAL OPERATIONAL INFORMATION

E-1 Us

in

g Both Voice and Data

Co

mmunications
E-2 High Speed/Low Speed Protocol
E-3 Retra

in

Sequence

E-4 PBX, De

di

cated Line, and Lease d Line

Opera tions

E-5 H

ew

lett Packard

In

sta

ll

a

ti

ons

E-1

COURIER HST
APPENDIX

E-1

USING BOTH VOICE AND

DATA

COMMUNICATIONS

PREPARATION

COMMANDS

E-1.1

When you assemble the Courier, you have the option

of

plugging your phone into the second modular jack

of

the

modem so

it

's available for voice calls. You can also use
the phone to synchronize communications with another
user whose modem uses the AT command set, such as

a USRobotics or USRobotics-compatible modem.

First call the other user to establish the bit rate, parity,

word length and number

of

Stop bits the other person's

modem accepts. Then both

of

you can turn the call over

to your modems.

I. Without hanging up the phone, have your modem go

off

hook

in

Originate Mode. Type the following command:

ATD

< er>

NOTE : Be sure the modem is not set

to

X2, X4, X6, or

X7,

or it will return the NO DIAL

TONE

result code and

hang up .

2.

The other party should then have the remote modem go
off

hook in Answer Mode. The following command

is

used to do this:

ATA

< er>

3. Now both

of

you can hang up your respective phones
while the two modems establish the data link. They will
maintain the link until one

of

you gives your modem a

command to disconnect.

Either party's device can be the originate

or

answer modem:

it

doesn't

matter who made the phone call. But one modem
must first enter Originate Mode and the other then enter
Answer Mode. You and the other party, therefore, must
agree on which command, ATD

or

ATA, you will each use.

NOT

E:

It

may happen that spurious

"garbage"

characters

will appear on the screen when you hang up the phone. You

can avoid these

by

hanging up the phone as soon as you

hear the modem go

off

hook, during the one

or

two seconds

it takes the two modems to establish the link.

OVERVIEW

COURIER HST

APPENDIX E-2

HIGH SPEED/LOW SPEED PROTOCOL

This appendix

is

intended for those users who want to try
programming their computers to switch bit rates to match
the Courier

HST's

connection rate. The material here applies

only when the modem

is

set for variable rates

at

both

the DTE (computer) and link interfaces,

&80

and &N0,

respectively.
In both Originate

or

Answer Modes, if the link rate

is

set

to

&N0 the Courier HST negotiates with the remote modem

to connect at the highest possible rate.

In

addition, if the

modem

is

set to the Extended or Advanced result codes

(XI or higher)

it

signals the DTE with one

of

the follow-

ing result codes or, unless the call

is

at

300 bps, an / ARQ

Mode equivalent:

CONNECT
CONNECT 1200
CONNECT 2400
CONNECT 9600

(300 bps)
(1200 bps)
(2400 bps)
(9600 bps)

The modem sends the result code at its previous rate. Then
it switches to the new connection rate.

If your computer doesn't switch rates and you want to pro­gram

it

to do so, use the example on the next page as a

guide.

It

demonstrates the occurrence

of

the CONNECT

codes

in

the connection sequence, so that recognition

of

the
codes can be used to switch the computer. The example uses
a sequence

of

incoming calls, but the codes apply to Origi-

nate Mode connections as well.

The example assumes the following settings:

Software: initially 9600 or 19.2k bps, allowing the full

range

of

link rates:

9600/2400/ 1200/300 bps

Modem: XI or higher (rate-specific CONNECT codes)

&80

(variable DTE rate)

&N0 (variable link rate)

E-2.1