Patton electronic 2720-I User Manual

USER
MANUAL

MODEL 2720/I

T1/Fractional T1 CSU/DSU
with Ethernet Bridging

An ISO-9001

Certified Company

Part# 07M2720I-UM
Doc# 08618U2-001,
Rev. C
Revised 10/05/07

SALES OFFICE
[phone]
TECHNICAL SUPPORT
[phone]
http://www.patton.com

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TABLE OF CONTENTS

Section

Page

1.0 Warranty Information .............................................................2

1.1 Warranty Statement

1.2 Radio and TV Interference

1.3 Industry Canada Notice

1.4 FCC Compliance

1.5 Service Information

2.0 General Information...............................................................5

2.1 Features

2.2 General Product Description

3.0 PPP Operational Background................................................6

3.1 Application

3.2 Configuration

4.0 Installation ..........................................................................31

4.1 Connecting the 10Base-T Ethernet Port to PC (DTE)

4.2 Connecting the 10Base-T Ethernet Port to a Hub

4.3 T1/FT1 Interface Connection

4.4 DC Power Connection

5.0 Operation.............................................................................33

5.1 LED Descriptions

5.2 Loop (V.54 & Telco) Diagnostics

5.3 Bit Error Rate (V.52) Diagnostics

Appendix A - Specifications ........................................................39

Appendix B - Ethernet 10Base-T Specifications ........................40

Appendix C - Factory Replacement Parts and Accessories ......41

Appendix D - T1 Interface Pin Assignments ..............................42

1.0 WARRANTY INFORMATION

Thank you for your purchase of this Patton Electronics product.
This product has been thoroughly inspected and tested and is warrant­ed for One Year parts and labor. If any questions or problems arise
during installation or use of this product, please do not hesitate to con­tact Patton Electronics Technical Support at [phone].

1.1 WARRANTY STATEMENT

Patton Electronics warrants all Model 2720 Series components

to be free from defects, and will—at our option—repair or replace the
product should it fail within one year from the first date of shipment.
This warranty is limited to defects in workmanship or materials, and
does not cover customer damage, abuse, or unauthorized modification.
This product contains no serviceable parts; therefore you should not
attempt to modify the unit in any way. If this product fails or does not
perform as warranted, your sole recourse shall be repair or replace­ment as described above. Under no condition shall Patton Electronics
be liable for any damages incurred by the use of this product. These
damages include, but are not limited to, the following: lost profits, lost
savings and incidental or consequential damages arising from the use
of or inability to use this product. Patton Electronics specifically dis­claims all other warranties, expressed or implied, and the installation or
use of this product shall be deemed an acceptance of these terms. In
the event that you detect intermittent or continuous product malfunction
due to nearby high power transmitting radio frequency equipment, use
only data cables with an external outer shield bonded to a metal or
metalized connector.

WARNING! This device is not intended to be con-

nected to the public telephone network in Europe.

1.2 RADIO AND TV INTERFERENCE

The NetLink-T1™ Model 2720 Series generates and uses radio
frequency energy, and if not installed and used properly—that is, in
strict accordance with the manufacturer's instructions—may cause
interference to radio and television reception. The Model 2720 Series
has been tested and found to comply with the limits for a Class A com­puting device in accordance with the specifications in Subpart J of Part
15 of FCC rules, which are designed to provide reasonable protection
from such interference in a commercial installation. However, there is
no guarantee that interference will not occur in a particular installation.
If the Model 2720 Series causes interference to radio or television
reception, which can be determined by disconnecting the cables, try to
correct the interference by one or more of the following measures:
moving the computing equipment away from the receiver, re-orienting
the receiving antenna, and/or plugging the receiving equipment into a
different AC outlet (such that the computing equipment and receiver
are on different branches).

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1.3 INDUSTRY CANADA NOTICE

The Canadian Department of Communications label identifies cer­tified equipment. This certification means that the equipment meets
certain telecommunications network protective, operational and safety
requirements. The Department does not guarantee the equipment will
operate to the user's satisfaction. Before installing this equipment,
users should ensure that it is permissible to be connected to the facili­ties of the local telecommunications company. The equipment must
also be installed using an acceptable method of connection. In some
cases, the company’s inside wiring associated with a single line individ­ual service may be extended by means of a certified connector assem­bly (telephone extension cord). The customer should be aware that
compliance with the above condition may not prevent degradation of
service in some situations. Repairs to some certified equipment should
be made by an authorized maintenance facility designated by the sup­plier. Any repairs or alterations made by the user to this equipment, or
equipment malfunctions, may give the telecommunications company
cause to request the user to disconnect the equipment. Users should
ensure for their own protection that the ground connections of the
power utility, telephone lines and internal metallic water pipe system,
are connected together. This protection may be particularly important
in rural areas.

1.4 FCC PART 68 COMPLIANCE STATEMENT

The Model 2720 Series has been tested and registered in compli­ance with the specifications in Part 68 of the FCC rules. A label on the
equipment bears the FCC registration number. You may be requested
to provide this information to your telephone company. Your telephone
company may make changes in its facilities, equipment, operations or
procedures that could affect the proper operation of the Model 2720
Series. If this happens, the telephone company should give you
advance notice to prevent the interruption of your service. The tele­phone company may decide to temporarily discontinue your service if
they believe your Model 2720 Series may cause harm to the telephone
network. Whenever possible, they will contact you in advance. If you
elect to do so, you have the right to file a complaint with the FCC. If
you have any trouble operating the Model 2720 Series, please contact
Patton Electronics Technical Support 301-975-1000. The telephone
company may ask you to disconnect the equipment from the telephone
network until the problem has been corrected or until you are certain
that the Model 2720 Series is not malfunctioning. In accordance with
FCC rules and regulation CFR 47 68.218(b)(6), you must notify the
telephone company prior to disconnection. The following information

CAUTION: Users should not attempt to make such connections
themselves, but should contact the appropriate electric inspection
authority, or electrician, as appropriate.

may be required when applying to your local telephone company for
leased line facilities. The Universal Service Order Code (USOC) is
RJ48. The Facility Interface Codes (FIC) are 04DU9-BN, 04DU9-DN,
04DU9-1KN, and 04DU9-1SN. The Service Order Code (SOC) is 6.0N.

Facility

Service Code Code Connection

1.544 Mbps SF format without line power 04DU9-BN 6.0N RJ48C

1.544 Mbps SF and B8ZS without line power 04DU9-DN 6.0N RJ48C

1.544 Mbps ANSI ESF without line power 04DU9-1KN 6.0N RJ48C

1.544 Mbps ANSI ESF and B8ZS w/o line power 04DU9-1SN 6.0N RJ48C

Interface Service Network

1.5 SERVICE INFORMATION

All warranty and non-warranty repairs must be returned freight
prepaid and insured to Patton Electronics. All returns must have a
Return Materials Authorization number on the outside of the shipping
container. This number may be obtained from Patton Electronics
Technical Support at: tel: [phone] email:
[e-mail] www: http://www.patton.com. NOTE:
Packages received without an RMA number will not be accepted.
Patton Electronics' technical staff is also available to answer any ques­tions that might arise concerning the installation or use of your Patton
Model 2720. Technical Support hours: 8AM to 5PM EST, Monday

through Friday.

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2.0 GENERAL INFORMATION

Thank you for your purchase of this Patton Electronics product.
This product has been thoroughly inspected and tested and is warranted
for One Year parts and labor. If any questions arise during installation or
use of the unit, contact Patton Electronics Technical Services at (301)
975-1007.

2.1 FEATURES

• Terminates T1/FT1 Circuits over a 4-Wire RJ-48C interface

• 10Base-T Ethernet bridge

• PPP (Point to Point Protocol, RFC 1661) with Bridge Control
Protocol (RFC 1638)

• Unstructured Rates at 1.544 Mbps

• D4 or ESF Framing Modes

• Supports AMI or B8ZS/B7ZS Line Coding

• Configuration via Software Control Port or Internal DIP Switches

• Six Easy-to-Read LED Indicators Monitor Data & Diagnostics

• Internal or Receive Recover Clocking

• Also Operates as a High-Speed Point-to-Point Modem

• Made in USA

2.2 GENERAL PRODUCT DESCRIPTION

The

NetLink-T1™

Model 2720/I is a single port T1/FT1 CSU/DSU

with Ethernet Bridging that provides high-speed LAN-to-WAN connectiv­ity. Plugging directly into the 10Base-T port of a hub or LAN switch, the
NetLink-T1™ provides T1 or FT1 access at connection data rates of

1.544 Mbps, nx64, and nx56 (n=1 to 24 channels). The Netlink-T1™ is
an excellent choice for internet access as well as LAN-to-LAN services.

The Netlink-T1™ provides digital access to a local WAN service
provider or directly between two facilities over a dedicated 4-Wire cir­cuit. WAN bandwidth, framing and coding options are programmed via
externally accessible DIP switches or via a VT-100 type terminal using
the rear-mounted EIA-232 Control Port. Netlink-T1™ supports D4/ESF
framing options and AMI/B8ZS/B7ZS line coding. Netlink-T1™ also sup­ports a full range of system and diagnostic features that make system
setup easy. The Ethernet Bridge in this unit requires no configuration at
all.

The NetLink-T1™ provides T1 terminations over a modular RJ-48C
jack and comply with jitter tolerance capabilities as specified in ANSI
T1.403 and AT&T TR62411. External power options include 120VAC and
universal interface 100-240VAC. 48VDC and rack card versions are also
available.

3.0 PPP OPERATIONAL BACKGROUND

PPP is a protocol used for multi-plexed transport over a point-to-point
link. PPP operates on all full duplex media, and is a symmetric peer-to-peer
protocol, which can be broken into three main components: 1. A standard
method to encapsulate datagrams over serial links; 2. ALink Control Protocol
(LCP) to establish, configure, and test the data-link connection; 3. A family of
Network Control Protocols (NCPs) to establish and configure different net­work layer protocols.

In order to establish communications over a point-to-point link, each end
of the PPP link must first announce its capabilities and agree on the param­eters of the link’s operation. This exchange is facilitated through LCP
Configure-Request packets.

Once the link has been established and optional facilities have been
negotiated, PPP will attempt to establish a network protocol. PPP will use
Network Control Protocol (NCP) to choose and configure one or more net­work layer protocols. Once each of the network layer protocols have been
configured, datagrams from the established network layer protocol can be
sent over the link. The link will remain configured for these communications
until explicit LCP or NCP packets close the link down, or until some external
event occurs.

The PPP Bridging Control Protocol (BCP), defined in RFC 1638,
configures and enables/disables the bridge protocol on both ends of
the point-to-point link. BCP uses the same packet exchange mecha­nism as the Link Control Protocol (LCP). BCP is a Network Control
Protocol of PPP, bridge packets may not be exchanged until PPP has
reached the network layer protocol phase.

3.1 APPLICATION

In situations where a routed network requires connectivity to a
remote Ethernet network, the interface on a router can be configured
as a PPP IP Half Bridge. The serial line to the remote bridge functions
as a Virtual Ethernet interface, effectively extending the routers serial
port connection to the remote network. The bridge device sends bridge
packets (BPDU's) to the router's serial interface. The router will receive
the layer three address information and will forward these packets
based on its IP address.

Figure 1 shows a typical Cisco router with a serial interface configured
as a PPP Half Bridge. The router serial interface uses a remote device that
supports PPP bridging to function as a node on the remote Ethernet net­work. The serial interface on the Cisco will have an IP address on the
same Ethernet subnet as the bridge.

For example, the customer site is assigned the addresses

192.168.1.0/24 through 192.168.1.1/24. The address 192.168.1.1/24 is
also the default gateway for the remote network. The above settings

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remove any routing/forwarding intelligence from the CPE. The associ­ated Cisco configuration will set serial interface (s0) to accommodate
half bridging for the above example.

Authentication is optional under PPP. In a point-to-point leased-line
link, incoming customer facilities are usually fixed in nature, therefore
authentication is generally not required. If the foreign device requires
authentication via PAP or CHAP, the PPP software will respond with
default Peer-ID consisting of the units Ethernet MAC address and a
password which consists of the unit’s Ethernet MAC address.

Some networking systems do not define network numbers in pack­ets sent out over a network. If a packet does not have a specific desti­nation network number, a router will assume that the packet is set up
for the local segment and will not forward it to any other sub-network.
However, in cases where two devices need to communicate over the
wide-area, bridging can be used to transport non-routable protocols.

Figure 2 illustrates transparent bridging between two routers over
a serial interface (s0). Bridging will occur between the two Ethernet
Interfaces on Router A (e0 and e1) and the two Ethernet Interfaces on
Router B (e0 and e1).

3.1.1 Switch S2

The table below shows the default configurations for Switch S2. A
description of all S2 options follows this table.

Switches S2-1, S2-2, and S2-3

Use Switches S2-1, S2-2 and S2-3 to set the DTE data rate.
Each setting represents an nx56/nx64 setting. Individual channel set­tings can be configured through the software control port.

S2-1

S2-2 S2-3 Speed
Off Off Off Clear Channel (Unframed)
On Off Off 112kbps/128kbps
Off On Off 224kbps/256kbps
On On Off 336kbps/384kbps
Off Off On 448kbps/512kbps
On Off On 672kbps/768kbps
Off On On 896kbps/1024kbps
On On On 1344kbps/1536kbps

Switch S2-4: Line Framing and Coding

Use Switch S2-4 to control the Network Line Framing and Coding

Options. Set these options to be the same as the Line Framing and
Coding Options given to you by your Service Provider. If you are using
two Model 2720s together as short range modems, set both units iden­tically.

Patton
2720
Bridge

Ethernet LAN

PEC Device w/ Serial I/F

Figure 1. Cisco router with serial interface, configured as PPP Half Bridge.

Router

S2-4 Line Framing & Coding

Off ESF/B8ZS
On D4/AMI

Line Framing Options:

D4/Superframe: The D4 framing format, as specified in AT&T

TR62411 is the standard in which twelve frames make up a
superframe. All signaling and synchronization are done in­band.

Extended Superframe (ESF): Extended Superframe, as speci-

fied in AT&T TR 54016, consists of twenty-four (24) T1
frames. The framing bits are now used for framing, CRC and
the Facility Data Link (FDL). The FDL allows maintenance
messages and information to be passed between the 2720
and the Central Office.

Line Coding Options:

Alternate Mark Inversion (AMI): This mode does not inherently

account for ones density. To meet this requirement, each time
slot can be reduced to 56 kbps and the Least Significant Bit
(LSB) of each time slot set to one.

!
no ip routing
!
interface Ethernet0
ip address 1.1.1.1 255.255.255.0
bridge-group 1
!
interface Serial0
ip address 1.1.1.1 255.255.255.0
encapsulation PPP
bridge-group 1
!
interface Serial1
ip address 2.2.2.2 255.255.255.0
bridge-group 1
!
bridge 1 protocol ieee
!

Figure 2. Transparent bridging between two routers over a serial interface.

Bipolar 8 Zero

Router A

S1

LAN

Router B

LAN

S1

e0

LAN

8

Serial Interface

S0

e0

Using Bridge-Groups, multi­ple remote LANs can be
bridged over the wide-area.

S0

e1

Serial Interface

2720/I

T1/FT1 Link

LAN

LAN

2720/I

T1/FT1 Link

Substitution (B8ZS): This mode assures proper bit density
in the data stream. In this mode any data pattern can be
transmitted without causing ones density errors. This mode
allows for 64 kbps clear channel timeslots.

Switch S2-5: DS0 Channel Rate

Use Switch S2-5 to set the DS0 rate.

SW2-5

Setting
Off 56 kbps
On 64 kbps

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S2 SUMMARY TABLE

Position Function Factory Default Selected Option

S2-1 Data Rate On

S2-2 Data Rate On

S2-3 Data Rate On

S2-4 Framing & Coding Off

S2-5 DS0 Rate On

S2-6 Clock Mode Off

S2-7 Clock Mode Off

S2-8 Reserved Off

1.536 Mbps
(DTE Rate)

ESF/B8ZS

64 kbps

Network

Reserved

Network

Switch S2-6 and S2-7: Clock Mode

Set Switch S2-6 and S2-7 to determine the 2720’s transmitter tim-

ing.

S2-6

Off Off

On Off

NOTE 1: When using the Model 2720 as a high-speed short
range modem, one unit of the link must be configured in Internal
Clock mode, and the opposite end unit must be configured for
Network Clock mode.

If the ERR LED on the front of the unit is flashing (or on) it could
be an indication of a clocking problem. Double check your clock
mode settings and Tx Clock Invert S1-3 settings.

Switch S2-8 Reserved

S2-7

Clock Mode

Network Clock

derived from the received line signal.

Internal Clock

derived from an internal oscillator.

. Transmitter timing is

. Transmitter clock is

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3.1.2 Switch S1

The chart below shows the default configurations for Switch S1. A
description of all S1 options follows this table.

Switch S1-1: RDL Type

Switch S1-1 selects the type of Remote Digital Loopback that the
2720 will initiate when the RDL is initiated from this unit. The 2720 will
respond to both the V54 and the CSU loopback regardless of the set­ting of S1-1

S1-1

RDL Type
On Initiate a V.54 RDL loop when selected
Off Initiate a CSU loopback when selected

Switch S1-2: Reserved

Switch S1-3: Tx Clock Invert

Switch S1-3 allows the user to invert the transmit clock originating

in the 2720. When S1-2 is set for transmit clock, it may be necessary
to invert the transmit clock to allow for delays due to long cables.

S1-3

Tx Clock Invert
On Transmit clock is inverted
Off Transmit clock is normal

Switches S1-4 and S1-5: Line Build Out

Use Switches S1-4 and S1-5 to set the Line Build Out (LBO). The

Line Build Out varies the pulse shape and attenuation of the signal
sent to the network. The amount of Line Build Out depends on
NetLink™ T1’s distance to the last repeater. The telephone company
providing the service will advise on the amount of LBO necessary. In
most cases the default setting will suffice.

SW1-4

SW1-5 Function
Off Off (0dB)
On Off -7.5dB
Off On -15.0dB
On On -22.5dB

Switch S1-6 Through S1-8: Reserved

3.2 SOFTWARE CONFIGURATION

The Model 2720 features a menu-driven command system that

allows you to monitor/configure its operating parameters. Follow the
instructions below to configure the Model 2720 using the software
selections:

S1 SUMMARY TABE

Position Function Factory Default Selected Option

S1-1

S1-2

S1-3

S1-4

S1-5 Off

S1-6

S1-7

S1-8 Reserved Off

1) Plug the 9-pin male end of the cable to your terminal or com-

puter’s DB-9 serial port and start up the terminal emulator
software if necessary. Plug the miniature stereo plug into the
rear of the unit. The small recessed jack on the left side of
the unit is the control port jack.

RDL Type

Reserved

Tx Clock Invert

Line Build Out

Reserved

Reserved

On

On

Off

Off

Off

Off

V.54 RDL

Normal

0dB

NOTE: If your terminal uses a DB-25 connector, please use a
DB-9 to DB-25 Adapter to connect to the cable.

2) Power up the terminal and set its RS-232 port as follows:

9600 Baud

8 data bits, 1 stop bit, no parity

Local echo off

ANSI or VT-100 emulation

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3) Here is an example of a terminal emulator setup session. In

normal font are the various parameter types. In bold type are
the values that should be used for best results. Your terminal
program’s setup screen may differ from this one:

Clocking: Network

(default)

Options: Network, Internal, External

Network: This is the most commonly used setting when connect

ing to a carrier’s network. In this mode, the unit recovers the
clock from the received signal and uses it to transmit data. In
this way the unit remains synchronized to a master clock.
Incampus applications, one of the units must be set to Internal
clock, and the other end is set to Network clock. At all times,
there must be only one clock source. Otherwise, clock slips
and framing errors and bit errors may occur.

Internal: This is commonly used in campus applications, where

the unit is not connected to the public telephone network
directly. In this mode, the unit uses the on-board oscillator as
the transmit clock source.

Line Build Out (dB): 0 – 133 feet, 0 dB

(default)

Options: -7.5 dB

-15.0 dB

-22.5 dB

This controls the transmitter signal strength and pulse shape. For

most applications, the default setting will suffice. When connecting to a
carrier connection, the carrier will determine what LBO is necessary.
0dB provides the highest signal strength and therefore the longest dis-

Baud rate: 9600 Parity: None Data Length: 8 Stop Bits: 1

Default terminal type: VT100
Local Echo: Off
Add Line Feeds after CRs: Off
Received Backspace Destructive: On
Backspace key sends: BS
XON/XOFF software flow control: On
CTS/RTS hardware flow control: Off
DSR/DTR hardware flow control: Off

tance, while –15.0 dB provides the lowest usable signal strength. The
last setting, –22.5 dB, is usually only used to test the line and should
not be used in normal applications.

4) When the unit is first turned on, the terminal screen may

appear blank. Press the [Enter] key. If your serial connection
is good, the unit will immediately display a password prompt.
The following message will appear in the middle of the
screen:

Patton Electronics
Menu Management

Enter Password: _

5) Type in the password and press [Enter]. The factory default

password for the unit is (password is case sensitive):

patton

NOTE: If the entry is incorrect, the password screen will clear
and prompt you again for the correct password. The password
you enter will not be shown. For security, asterisks will be dis­played for each letter you type. The maximum length of the
password, which can include any character the terminal can
generate, is 16 characters.

6) The Model 2720 will then display the Main Menu screen.

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3.2.1 Introduction to Main Menu

After entering the password, you may access all of the system’s

functions and parameters. The Main Menu looks like this:

HELPFUL HINTS

1. To make a selection, key the highlighted letter that corre-

sponds to a menu selection.

2. To execute the selection, type [Enter/CR]

3. To toggle between options on a highlighted selection, Press

[space].

4. Select Save Changes from Main Menu after making modi-

fications to any Model 2720 parameter. Otherwise, changes
will be lost when the Model 2720 is turned off.

d

The Main Menu options are briefly described below.

a

System Configuration options allow you to change various
aspects of the Model 2720’s operation, e.g., framing, line cod­ing, and aggregate bandwidth.

System Diagnostics/Statistics options allow you to monitor

b

the network performance, initiate V.54 loops, local loops, and
send test patterns. Network performance parameters are
updated once a second, giving you the ability to quickly deter­mine if there is a problem.

Unit Options allow you to customize the Model 2720 for your

c

location. You can change the default header names to give
each unit a unique name and password. Also, you can reset
the unit to its default settings without the manual. It also has a
Service Information screen in case you need technical assis­tance from Patton Electronics.

Save Changes. Once you have configured the unit to your

d

satisfaction, you can save the changes permanently by exe­cuting the Save Changes command. This will update the unit’s
configuration and save all the parameters to permanent mem­ory.

Logoff. For security, log off the control menu by executing

e

the Logoff command. This will blank the screen until an
[Enter] key is pressed.

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3.2.2 System Configuration

The default System Configuration menu looks like this:

The System Configuration options are described below:

Line Format: ESF

(default)

Options: ESF, D4, UNFRAMED

D4: This is an older, but widely used, line format that does not

provide FDL, so network interface performance cannot be
monitored so easily. AT&T TR 62411 contains the specifica­tions for this format and the ESF. D4 is also known as
Superframe format. According to TR 62411, “The Superframe
format…consists of 12 frames of 193 bits each for a total of
2316 bits. Each 193 bit frame consists of 192 bits preceded
by one framing bit….the framing bit is time shared to both
synchronize the terminal equipment and to identify the signal­ing frames.” (Sec. 4.1.1)

ESF: This stands for Extended Superframe Format, a line format

developed by AT&T. AT&T Technical Reference 54016 (TR

54016) defines the ESF, a format which is commonly used to
allow monitoring of the network interface performance over
the Facility Data Link (FDL). AT&T TR 62411 says, “the

Extended Superframe Format “extends” the DS1 superframe
structure from 12 to 24 frames…for a total of 4632 bits. It
redefines the 8 kb/s channel previously used exclusively for
terminal and robbed bit signaling synchronization.” The ESF
provides a 4 kb/s data link, called the FDL, which allows for
in-service monitoring and fast troubleshooting. Certain net­work services require the ESF.

UNFRAMED:This is a special mode that allows you to achieve the

maximum possible data rate of 1.544 Mb/s (million bits per
second) by using the framing bits for data transmission. There
is no signaling or FDL. This is commonly used for campus
connections, and by the Federal government and the military.
This format is not to be used when connecting to a public car­rier’s network without its permission. This provides one chan­nel at a rate of 1.544 Mb/s. In addition, this format can be
used with external clocking.

Line Coding: B8ZS

Options: AMI, B8ZS, B7ZS.

AMI: Alternate Mark Inversion defines a pulse as a “mark”, a

binary one, as opposed to a zero. In a T1 (DS1) network con­nection, signals are transmitted as a sequence of ones and
zeros. Ones are sent as pulses, and zeros are sent as
spaces, i.e., no pulse. Every other pulse is inverted from the
previous pulse in polarity, so that the signal can be effectively
transmitted. This means, however, that a long sequence of
zeros in the data stream will cause problems, since the
CSU/DSU receiving the signal relies on the signal to recover
the 1.544 Mb/s clock. To get around this problem, one method
is to limit the data rate per channel (known as a DS0,
because it is a 64 kb/s portion of the DS1 frame or super­frame) to 56 kb/s and forcing a pulse in the last data bit to
ensure a minimum pulse density in the signal. If you must use
AMI with a DS0 data rate of 64 kb/s, you should ensure that
the data terminal equipment connected to the unit provides a
minimally acceptable pulse density. For this reason, there are
advantages to using B8ZS instead.

B8ZS: Bipolar violations occur when consecutive pulses are of

the same polarity. In B8ZS, or Bipolar Eight Zero Substitution,
bipolar violations are introduced deliberately to indicate that
eight zeros have been transmitted. This special encoding is
recognized by the receiver and decoded correctly. See AT&T
TR62411 Section 4.2.2 for a detailed description of B8ZS.

(default)

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This enables information to be sent over a T1 connection
without any constraints on the data’s pulse density. This is the
most acceptable way to accomplish 64 kb/s on each DS0
channel.

B7ZS: This stands for Bipolar Seven Zero Substitution. Instead of

introducing bipolar violations, this method substitutes a one
for a zero in bit 7 (out of 8) of a DS0 channel when the data in
that channel are all zeros. This is a special form of AMI and is
compatible only with special equipment. For most applica­tions, AMI or B8ZS will suffice.

DS0 Line Rate: 64kbps

(default)

Options: 64kbps, 56kbps

64kbps: Also known as Clear Channel, this takes full advantage

of the available bandwidth in a DS0 channel. Implementing it
usually requires B8ZS line coding. In certain cases, special
equipment may implement Clear Channel using AMI or B7ZS.
Consult the equipment manual for compatibility. Your carrier
will advise you on whether to use 64 or 56 kb/s. Campus
applications may not have such restrictions, enabling you to
use 64kbps. In Unframed format, the 24 DS0s and the fram­ing bits are combined to provide 1.544Mb/s for your use.

56kbps: This uses only the first seven bits of the DS0, limiting the

data rate per DS0 channel to 56 kb/s. Your carrier will advise
you on whether to use 64 or 56 kb/s. This is not available
when using the Unframed format.

ESF Data Link: ANSI T1.403

Options: ANSI T1.403, AT&T TR54016

ANSI T1.403: This ANSI developed standard (see ANSI T1.403-

1995: Network-to-Customer Installation—DS1 Metallic
Interface) uses the FDL to send and receive one second
Performance Report Messages (PRMs). The messages con­tain the NI performance over the last four seconds. Thus, up
to three consecutive messages may be lost without loss of
information. It is available only with ESF. When ANSI T1.403
is selected, requests to send AT&T performance reports (ref.
AT&T TR 54016) are ignored.

AT&T TR54016: Developed by AT&T, this FDL method differs

principally from the ANSI method in two ways: First, the ANSI
method transmits messages continuously, whereas the AT&T
method transmits a performance report only upon a request
from the remote end for a report. Second, the AT&T method
provides a historical summary, up to the last 24 hours, of NI
performance. Only the service provider or special test equip­ment can send these requests. When AT&T TR54016 is
selected, ANSI PRMs are still transmitted by the unit, but only
PRMs sent by the carrier will be recognized. To receive PRMs
from another customer unit (i.e., in a campus application),
select ANSI T1.403. When the frame is not ESF, the FDL is
disabled.

(default)

ESF Carrier Loops: Enabled

Options: Enabled, Disabled

The ESF format provides the CO the ability to put the customer

installation’s Model 2720 into loopback mode. The Model 2720 recog­nizes these special messages that are sent over the FDL. When
enabled, the unit will respond to these loopback commands and go into
or out of loopback mode. When disabled, the unit will not respond,
although it still recognizes the loopback commands. When in loopback,
the unit will remain in loopback until a loopback exit command is
received or when the loopback timer times out. See Unit Options
(Section 3.2.4) to make Loop Timeout choices. This feature allows the
remote user to regain control should one be locked out after a loop­back is initiated.

(default)

20

21

Remote In-band Loops: Enabled

(default)

Options: Enabled, Disabled

In ESF, D4 and Unframed formats, the unit can respond to special

repeating codes in the data stream that represent loopback com­mands. The command to loop up (go into loopback) is a repeating pat­tern of 00001s. This pattern overwrites the normal data. When this
code is detected for 5 seconds, the unit will go into loopback if the
Remote In-band Loopback is Enabled. When a repeating code of 001s
is received for 5 seconds, the unit loops down (goes out of loopback).
The delayed recognition guards against false starts, since the code
must be present for a long time continuously. When Disabled, the unit
will recognize the codes but will not respond to them. The loopback
timeout also applies to this feature.

V.54 Loops (RDL Only): Enabled

(default)

Options: Enabled, Disabled

This is a special in-band loopback facility that sends a special

pseudo-random pattern over the data stream. This is the only remote
loopback that the unit can initiate. This is useful for campus applica­tions when you need to put a remote unit in loopback. The remote unit
responds to the V.54 loopback command, and the whole process takes
only a few seconds to complete. This setting will enable/disable RDL
from being initiated from either the control port or the DTE interface. It
will also enable/disable the unit to respond to the V.54 command if
received over the line. The duration of the loopback is limited by the
loopback timeout setting. (See Unit Operations, paragraph 3.2.4, on
pages 32 and 33.)

Default Config Source: Switch (default)

Option: EEPROM, Switch

The Model 2720 can be initialized via the configuration in the on-

board permanent memory (EEPROM) or via the internal DIP switches
(Switch). Once the unit is powered up, you may change the settings
through the control port or the DIP switches.

If you do not have a terminal, you may force the unit to use the

DIP switches as the default configuration source by turning off the unit,
setting all the DIP switches to the ON position, then powering on the

unit. This will cause the unit to enter a special mode. Then turn off the
unit and change the switch settings to the desired settings. When you
turn the unit on again, the unit will be set up with the selected switch
settings.

DS0 Channel Configuration Menu: [ Bandwidth/# Channels =
1,536/24 ]

The DS0 Channel Configuration Menu has a sub-menu that looks
like this:

You may configure the Model 2720 to operate with any combina-

tion of active and inactive DS0 channels in this screen. When you exe­cute the Save Changes command, the selected settings will be saved
to permanent memory, and the system will be updated to operate with
the new channel settings.

NOTE: In Unframed format, the Bandwidth Selected will display
“1,544k,” and the Total Channels will display “n/a.” When the DS0
Channel Rate is 56kbps, the Bandwidth Selected will be a multiple
of 56k, not of 64k. When using the DIP switches to set the band­width, the starting channel is always channel 1.

3.2.3 System Diagnostics

(default)

The System Diagnostics/Statistics screen looks like this:

NOTE: This screen is updated once per second.

The System Diagnostics/Statistics options and functions are

described below.

Local Loop: Idle

The Local Loop is a bi-lateral loopback in which the data from the

local DTE and the data from the remote unit are looped back to their
respective sources (See Section 5.3). Activate this loop to test the
each of the DTE’s connection to the Model 2720.

The Local Loop test has four states:

Idle No user-controlled loopbacks are active.

LL The Model 2720 is in local loopback mode.

(default)

22

23

Off The Model 2720 is in remote or CO initiated loopback

mode or sending a pattern. Local loopback is disabled.

LocP The Model 2720 is in Local Loopback mode, and is send-

ing a test pattern.

Remote Loop Idle

(default)

The Remote Digital Loopback (RDL) test checks the performance

of both the local and remote Model 2720s, as well as the communica-

tion link between them. Data from the local DTE is sent across the
entire communication circuit and looped back to the local DTE.

The Model 2720 Initiating a RL can be in one of the following

states:

Idle No user-controlled loopbacks are active.

TxPr The Model 2720 is sending the preparatory phase pat-

tern lasting for approximately 2 -5 seconds.

WtAk The Model 2720 is waiting for an acknowledgement from

the remote unit. If the remote unit does not respond, the
WtAk message will remain on the screen.

RxAk The Model 2720 has received an acknowledgement from

the remote unit.

Tout The Model 2720 is waiting before entering the Remote

Loopback test mode.

TM The Model 2720 has successfully negotiated the Remote

Loopback test and is in control of the remote unit. You
may send a test pattern at this point by pressing:

c <spacebar>

TxTr The Model 2720 is sending a Terminate Loopback mes-

sage to the remote unit. If the remote unit does not
respond, the local unit will return to the Idle state.

Tx1s If the remote Model 2720 responds to the local NetLink-

T1™’s terminate loopback request, the local unit then
sends an all ones pattern before returning to the Idle
state

TxP The Model 2720 is sending a test pattern while in Test

Mode

IdlP The Model 2720 is sending a test pattern in place of

data. The Model 2720 is not in test mode.

24

25

The Model 2720 receiving a RL can be in one of the following states:

RxPr The Model 2720 is receiving a preparatory pattern.

Sack The Model 2720, upon receiving a preparatory pattern,

sends an acknowledgement message.

RL The Model 2720 is in remote loopback mode.

RxTr The Model 2720 is receiving a terminate loopback mes-

sage.

Wt1s The Model 2720 is waiting for a sequence of all ones and

will time out if it does not receive it.

IdleP The Model 2720 is sending a QRSS, 511 or 2047 pattern.

Off The Model 2720 is in local loopback.

Test Pattern Idle

(default)

Options: Idle or Sending

To send a pattern, press the ‘c’ key and press <spacebar> to send

the test pattern. The “OK” message indicates the received test pattern
is error-free. The “BE” message indicates errors in the received pat­tern.

Idle Indicates that Model 2720 is not sending a pattern.

Sending Indicates that 2720 is sending a pattern.

Error Insertion Off

(default)

Options: On, Off

You may inject intentional errors into the test pattern by turning

Error Insertion ON. The Error (ERR) LED will blink once per second.

Selected Pattern

Options: QRSS, 511, or 2047

Use this option to select the test pattern used to test the link.

NI STATUS

The Network interface (NI) status is shown
in the middle of the Diagnostics/Statistics screen. The brackets are
empty when the link is operating normally. In this example, various two
or three-letter messages are displayed within the brackets, illustrating
what you may see if the Model 2720 is not connected at all or is in a
loss of signal condition. Here are the eight status messages.

Excessive zeros [EXZ], i.e., lack of pulses, detected. This condition
may occur if the unit is not connected to the network, in which case the
EXZ is displayed continuously. If EXZ comes on intermittently, there
may be a frame, line code or data rate mismatch between the near and
far-end units.

Receiver Carrier Loss [RCL] occurs when 192 consecutive zeros
have been detected at the network interface. RCL clears when a pulse
is detected.

Frame Bit Error [FE] occurs when there is an error in the framing bit
sequence. This may happen due to a disconnected line, mismatched
framing formats or severe errors in the data stream. This error may
indicate a noisy line or cable condition. This error may indicate a noisy
line or cable connection if the frames appear to be set correctly.

Severe Frame Error [SE] occurs when the framing error exceeds a
certain threshold of errors. This may happen due to a disconnected
line, an extremely noisy connection, or mismatched framing.

Loss of Sync [LOS] occurs when the T1 framer in the unit cannot
synchronize itself to the received data stream. This may happen due to
a disconnected line.

Out of Frame [OOF] occurs when no valid frame structure can be
found. This may happen due to a disconnected line or mismatched
framing or mismatched framing.

Alarm Indication Signal [AIS] indicates that the remote unit or the
central office is sending a Blue Alarm, because it is not receiving a sig­nal; the alarm is an unframed all-ones signal, mainly used to keep the
line alive and to indicate that it is not receiving any signal. This may
indicate that the local unit is receiving a good signal, but that the trans­mit link may be broken.

Receive Alarm Indication [RAI] indicates that the local unit is receiv-

26

ing a Yellow Alarm. This alarm is sent by
the remote unit or the central office when it
loses the received signal. This indicates the
local unit’s transmitted signal is not reach­ing the remote unit.

Rx Level The Model 2720 displays the
current received signal strength in dB.
There are four level ranges detected:

+2 to –7.5

-7.5 to –15

-15 to –22.5
< -22.5

Valid Interval Count & Current Interval Time

The Valid Interval Count and Current Interval Time display the

number of valid 15 minute intervals in the last 24 hours and the num­ber of seconds which have elapsed in the current interval, respectively.
The Valid Interval Count saturates at the count of 96 (96 * 15min = 24
hours), while the Current Interval Time rolls over after 900 counts.
When the counter rolls over, it is reset to zero, and the Interval Counter
is incremented by one if the count is less than 96.

Error Counters

These error counters give a second-by-second snapshot of the

link performance. To clear all counters, press the [Backspace] key. If
your keyboard does not have this key, you can press a two-key combi­nation to affect the same result: Hold down the [Ctrl] key and then
press the [H] key. This will send to the unit the Ctrl-H character, which
is the same as pressing the [Backspace] key.

27

Rx PRM

The NetLink-T1™ transmits ANSI performance report messages

once a second when the framing mode is ESF. When the ESF Data
Link is set to ANSI T1.403, the unit recognizes PRMs with addresses
of 38h or 3Ah. The address 3Ah indicates the PRM is coming from a
Carrier, whereas the address 38h indicates the PRM is coming from a
Customer. When the ESF Data Link is set to AT&T TR54016, the unit
recognizes Carrier-originated PRMs, which have an address of 3Ah.

Rx PRM: 00010000000300023289

Current DIP Switch Settings

The Switch settings are displayed here to
facilitate troubleshooting your unit without
opening up the unit first.

Switch

1: On
2: On
3: On
4: Off
5: On
6: Off
7: Off
8: Off

28

29

3.3.6 Unit Information

The Unit Options screen looks like this (factory default):

Header Line 1 & Header Line 2

Headers 1 and 2 are provided for easy identification of your unit

after installation. You may want to give each unit a unique name via
the header lines to help distinguish one unit from another. You can
enter a header up to 40 letters long. Two lines provide 80 letters for
your use. That’s a lot of flexibility!

Password

The Password facility provides security by allowing only those who

know the correct password to configure the unit via the control port.
You can still configure the unit via the DIP switches. The password can
be up to 16 characters long, with no restriction on the combination of
characters you can use, so be sure to remember the password. If you
lose your password, you will lose the ability to access the unit via the
control port.

Loop Timeout

The Loop Timeout setting can be set to one of the following:

00:05 = five minutes
00:10 = ten minutes
00:15 = fifteen minutes
00:30 = thirty minutes (default setting)
00:45 = forty-five minutes
01:00 = one hour
01:30 = 90 minutes
02:00 = two hours
03:00 = three hours
NEVER = forever—the unit will remain in loopback without user

intervention.

Tx Data Clock

This option selects the clock that is used to accept the Transmit

Data from the DTE interface. Standard DTE interfaces will transmit
data with respect to the External Clock. In some cases a DTE interface
will transmit with respect to the Transmit clock sent out from the 2720.
Please review the information provided with your DTE equipment for
more information on its' operation. In most cases when there are errors
on the line only in the direction of the transmit data either Tx Data
Clock or Tx Clock Invert can be changed to solve the problem.

Tx Clock Invert

This option allows the user to invert the transmit clock originating

in the 2720. When Tx Data Clock is set for transmit clock, it may be
necessary to invert the transmit clock to allow for cable delays.

Set to Default Configuration

You may set the NetLink-T1™ to its factory default configuration,

except for the header lines and the password, by executing the Set to
Default Configuration command.

30

44..00 II NNSSTTAA LLLL AA TT IIOO NN

The Model 2720 is equipped with DTE, network, and power inter-

faces. This section briefly describes connection to each.

4.1 Connecting the 10Base-T Ethernet Port to a PC (DTE)

The 10Base-T Interface is configured as DTE (Data Terminal
Equipment). If the Model 2720/I is to to connect to another DTE
device such as a 10Base-T network interface card, construct a
10Base-T crossover cable and connect the wires as shown in the dia­gram below (Figure 4).

10BaseT Port 10Base-T DTE
RJ-45 Pin No. RJ-45 Pin No.

1 (TD+) 1 (TD+)
2 (TD-) 2 (TD-)

3 (RD+) 3 (RD+)
6 (RD-) 6 (RD-)

4.2 Connecting the 10Base-T Ethernet Port to a Hub

The 10Base-T interface is configured as DTE (Data Terminal

Equipment), just like a 10Base-T network interface card in a PC.

Figure 4: 10Base-T Cross-over Cable Connection

31

1 TD+ (data output from 2720/I)
2 TD- (data output from 2720/I)
3 RD+ (data input to 2720/I)
4 (no connection)
5 (no connection)
6 RD- (data input to 2720/I)
7 (no connection)
8 (no connection)

1
2
3
4
5
6
7
8

Figure 3: Connecting the 10Base-T Ethernet Port to a PC

Control

Port

T1 Interface

10BaseT Interface

Therefore, it “expects” to connect to a 10Base-T Hub using a straight­through RJ-45 cable. Use the diagram below (Figure 9) to construct a
cable to connect the 10 BaseT interface to a 10Base-T Hub.

10BaseT Port 10Base-T Hub
RJ-45 Pin No. RJ-45 Pin No.

1 (TD+) 1 (RD+)
2 (TD-) 2 (RD-)

3 (RD+) 3 (TD+)
6 (RD-) 6 (TD-)

Figure 5: Connecting the 10Base-T Ethernet Port to a Hub

4.3 T1/FT1 INTERFACE CONNECTION

The Network Line Interface Line is an eight position keyed modu-

lar jack configured as a RJ-48C. This interface will need to be config­ured to match the line parameters (i.e. framing, line coding, etc.) sup­plied by the central office.

1 RX Data (TIP)

1

2

3

4

5

6

7

8

2 RX Data (RING)
3 (no connection)
4 TX Data (TIP)
5 TX Data (RING)
6 (no connection)

} From Network

} To network

7 (no connection)
8 (no connection)

Figure 6. Model 2720 twisted pair line interface.

NOTE:

If the Model 2720 is being used for private short range
modem applications, the twisted pair cable connected to
its port will need to be a crossover cable. See Appendix
D for Interface pin assignments.

4.4 DC POWER CONNECTION

The 36-60 VDC DC to DC adapter is supplied with the DC version
of the Model 2720. The black and red leads plug into a DC source (nom­inal 48VDC) and the barrel power connector plugs into the barrel power
supply jack on the 2720.

To Power

Supply Jack

Barrel power connector

-Vin

+Vin

To -48VDC

Source

Black lead (-V)

Red lead (+V)

32

33

55..00 OO PP EE RR AATT IIOO NN

Once the NetLink-T1™ is installed and configured properly it is

ready to place into operation. This section describes the function of
the LED indicators, and the use of the loopback and pattern test
modes.

5.1 LED DESCRIPTIONS

The NetLink-T1™ is equipped with six LED indicators that monitor

the status of communication. Figure 12 (below) shows the location of
the LEDs on the NetLink-T1™ Series front panel.

T1 Link Solid green indicates that the end to end TI

link is up. Signifying that the link is active.
The TI link LED is off when the link is down

10BT Link (Active Green) Solid green indicates that

the 10BaseT Ethernet interface has detect
ed a valid SQE heartbeat, signifying a valid
10BaseT connection.

Status Blinks yellow from one to eleven times to

indicate system status. Each pulse pattern
is separated by a 2 second “off” period.

Greater pulse patterns have higher priority
(buffer saturation has greater priority than an
empty MAC table). Valid system statuses are:

1 pulse = system status is okay
2 pulses = no MAC entries in the

MAC Address Table

3 pulses = Clear to Send (CTS) or

Carrier Detect (DCD) from

base unit are not asserted
4 pulses = IM1/I buffer is saturated
5 pulses = WAN receive frame(s) too large
6 pulses = WAN receive frame(s) not octet

aligned

7 pulses = WAN receive frame(s) aborted
8 pulses = Detected WAN receive frame(s) with

Figure 7: 2720/I Front Panel

10BaseT T1/FT1 CSU/DSU

9 pulses = Detected LAN receive frame(s) too

10 pulses = Detected LAN receive frame(s) not

11 pulses = Detected LAN receive frame(s) with

ALM The alarm LED indicates the presence of a

ER The error LED indicates various error condi-

CRC

large

octet aligned

bad CRC

Blue or Yellow Alarm, or Out of Frame con­dition. The ALM LED will blink on every half­second. Alarms may occur due to:

•

Loss of Synchronization

• Loss of Frame

• AIS (Blue Alarm)

• RAI (Yellow Alarm)

tions, including framing bit errors, excessive
zeros, controlled slips, severe errors, or bit
errors (when sending V.52 test patterns).
When sending a test pattern, the LED will
remain lit if the unit does not receive the
identical pattern. When it receives the cor­rect pattern, the LED will turn off. If error
insertion is on, the LED will blink once a
second if everything is operating properly.

TM The test indicator LED blinks with a specific

pattern depending on the type of test mode.
When the unit is in local analog loop, the
LED will blink on briefly. When the unit is in
remote loop, the TM LED will blink off
briefly. When the unit is sending a test pat­tern or is putting the remote unit into
V.54/CSU loopback, the TM LED will stay
on. These are the test modes:

• V.54/CSU Loopback & V.52 Patterns

• D4 Line Loop (CO initiated)

• ESF Line Loop (CO Initiated)

• ESF Payload Loop (CO Initiated)

34

35

5.2 LOOP (V.54 & TELCO) DIAGNOSTICS

The NetLink-T1™ offers three V.54 loop diagnostics and is com­patible with two Telco loop diagnostics. Use these diagnostics to test
the CSU/DSU and any communication links. These tests can be acti­vated via the software control port (See Section 3.2.3 System
Diagnostics), via signals on the serial port interface or the front panel
switch.

5.2.1 Operating Local Loopback (LL)

The Local Loopback (LL) test checks the operation of the local
NetLink-T1™, and is performed separately on each unit. Any data sent
to the local NetLink-T1™ in this test mode will be echoed (returned)
back to the user device (i.e., characters typed on the keyboard of a ter­minal will appear on the terminal screen).

To perform a LL test, follow these steps:

1. Activate LL. This may be done in one of two ways:

a. Enter Local Loop from the System Diagnostics/Statistics

menu and toggle the <Spacebar> until “LL” appears next
to the Local Loop option.

b. Toggle the front panel switch to the “Local” position.

2. Verify that the data terminal equipment is operating properly
and can be used for a test.

3. Perform a V.52 BER (bit error rate) test as described in
Section 5.3. If the BER test equipment indicates no faults,
but the data terminal indicates a fault, follow the manufactur­er’s checkout procedures for the data terminal. Also, check
the interface cable between the terminal and the NetLink-T1.

Figure 8. Local Loopback

Ethernet

Device

Ethernet

Device

Receive
Recover

Clocking

Internal

Clocking

Cable Span

T1/FT1 CSU/DSU

Model 2720/I

T1/FT1 CSU/DSU

Model 2720/I

Clock/
Data

Clock/
Data

Clock/
Data

Data

Data

Model 2720/X

Model 2720/I

LLB Initiated

5.2.2 Operating Remote Digital Loopback (RL)

The Remote Digital Loopback (RL) test checks the performance of
both the local and remote NetLink-T1™, as well as the communication
link between them. Any characters sent to the remote NetLink-T1™ in
this test mode will be returned back to the originating device (i.e, char­acters typed on the keyboard of the local terminal will appear on the
local terminal screen after having been passed to the remote NetLink­T1™ and looped back).

T1/FT1 CSU/DSU

Model 2720/I

Receive
Recover

Clocking

Data

x

Model 2720/I

Ethernet

Device

Clock/
Data

Clock/
Data

T1/FT1 CSU/DSU

Model 2720/I

Internal

Clocking

Cable Span

Model 2720/I

RL Initiated

Figure 9. Remote Loopback

There are two Remote Loops that can be initiated from the
NetLink-T1 unit: (1) V.54 Loop, and; (2) CSU Loop. The user can
select the type of loop that can be initiated from the System
Diagnostics/Statistics screen or with Switch S1-1. When a loopback
is initiated this is the type of loop that the unit uses to loop up the
remote unit. NOTE: The NetLink-T1 will respond to both loops regard­less of the state of the RDL Type.

To perform an RDL test, follow these steps:

1. Activate RDL. This may be done in two ways:

a. Enter Remote Loop from the System

Diagnostics/Statistics menu and toggle the <Spacebar>
until “RL” appears next to the Remote Loop option.;

Ethernet

Device

Clock/
Data

Data

b. Set the front panel switch to ‘Remote’.

2. Perform a bit error rate test (BERT) using the internal V.52

generator (as described in Section 5.3), or using a separate
BER Tester. If the BER test indicates a fault, and the Local
Line Loopback test was successful for both NetLink™s, you
may have a problem with the twisted pair line connection.

36

5.2.3 CSU Loop

The NetLink-T1™ also responds to central office initiated loop com­mands. The NetLink-T1™ will implement the “loop up” command when
it recognizes the pattern “10000” in the data stream for a minimum of 5
seconds. The “loop down” command is implemented by the pattern
“100” in the data stream for a minimum of 5 seconds.

When operating in ESF framing mode, loopback commands are
issued via the Facility Data Link (FDL). The line loop message will
cause a loop back before data enters the framer portion of the CSU.
The payload loop message will cause the NetLink-T1™ to loop data
after the framer portion of the CSU.

The NetLink-T1™ will respond to Universal Loopback De-activate
to clear all central office loops.

5.3 BIT ERROR RATE (V.52) DIAGNOSTICS

The NetLink-T1™ offers three V.52 Bit Error Rate (BER) test pat­terns. These test patterns may be invoked along with the LAL and
RDL tests to evaluate the unit(s) and the communication links.

When a 511, 2047, or QRSS test is invoked, the NetLink-T1™
generates a pseudo-random bit pattern of 511 bits, 2047 bits or 2

20

bits, respectively, using a mathematical polynomial. The receiving
NetLink- T1™ then decodes the received bits using the same polyno­mial. If the received bits match the agreed upon pseudo-random pat­tern, then the NetLink-T1™(s) and the communication link(s) are func­tioning properly.

511 Initiates a built-in 511 bit pseudo-random

pattern generator and detector.

2047 Initiates a built-in 2047 bit pseudo-random

pattern generator and detector.

QRSS Initiates a built-in 2

20

bit pseudo-random

pattern generator and detector.

37

To perform a V.52 test, follow these steps:

1. Activate the local loopback or remote loopback diagnostic.

2. Activate the test pattern. This may be done in one of two
ways:

a. Enter Selected Pattern from the System

b. Enter Test Pattern and toggle the [Spacebar] to send

c. One of two result codes will appear to the right of the

e

Diagnostics/Statistics menu and toggle the <Spacebar>
until the desired test pattern appears.

c

the selected pattern.

Test Pattern listing:

OK Indicates that the received test pattern is error-free.

BE Indicates that there are errors in the test pattern (to

deliberately insert errors in the pattern, toggle

Error Insertion to ON).

38

39

APPENDIX A

PATTON NETLINK-T1 MODEL 2720

SPECIFICATIONS

WAN Speed: 1.544 Mbps

WAN Connection: RJ-48C

Nominal Impedance: 100 Ohms

DTE Interface: 10Base-T Ethernet (802.3)

Line Coding: AMI/B8ZS

Line Framing D4/ESF/Unframed

Receive LBO: Automatic

Transmit LBO: Selectable - 0, 7.5,

15, or 22.5 dB, plus DSX-1

Clock Options: Internal or network clock

Diagnostics: Responds to CO-initiated D4 loopup

and loopdown codes, ESF line loop
and payload loop FDL messages,
Universal Loopback De-activate mes­sage,V.54 Remote Loop, Local Loop,
and V.52 BER Patterns:
511,2047,QRSS

Standards: AT&T TR62411, TR54016, ANSI T1.403

Power Supply: 120VAC, 60 Hz to 5VDC 300mA wall-

mount transformer or UI 100-240VAC,
50-60 Hz to 5 VDC, 2A desktop trans­former

Dimensions: 3.5”L x 2.1”W x 0.78”H (9.0 x 5.3 x 1.9

cm)

5.0’’ L x 42’’ W x 1.5’’ H

APPENDIX B

ETHERNET 10BASE-T SPECIFICATIONS

DTE Interface: 10Base-T on RJ-45F

DTE Data Rates: 10Mbps

LAN Connection: RJ-45, 10Base-T, 802.3 Ethernet

Protocol: PPP (RFC 1661) with Bridging Control

(RFC 1638)

MAC Address Table Size: 4096 entries

MAC Address Aging: MAC addresses deleted after 8 min-

utes of inactivity

Frame Buffer: 512 Frames

Frame Latency: 1 frame

Indicators: T1 Link, 10Base-T Link, Ethernet

Status, Loss of Frame Sync, Error, Test
Mode

Humidity: Up to 90% non-condensing

o

Temperature: 0 to 50

C

40

APPENDIX C

PATTON NETLINK-T1™ MODEL 2720

FACTORY REPLACEMENT PARTS

AND ACCESSORIES

Patton Model #

Description

10 - 09F............................6 Foot Control Port Cable, 2.5mm to

DB9F

07M2720/I........................User Manual

2720/C/UI.........................T1 N x 64 CSU/DSU(M/34 female, UI)

2720/B/UI.........................T1 N x 64 CSU/DSU(DB25 female,UI)

2720/I/UI..........................T1 N x 64CSU/DSU(10BaseTEthernet,UI)

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APPENDIX D

PATTON NETLINK-T1™ MODEL 2720

INTERFACE PIN ASSIGNMENT

RJ-48C T1 (DS0) Network Interface

(Female Modular Jack)

Pin #

1 RX Data (TIP 1)
2 RX Data (RING1)
4 TX Data (TIP)
5 TX Data (RING)

Pin #

Tip Tx Data From Model 2720

Ring Rx Data To Model 2720

Sleeve Ground

RS-232 Control Port (Signals at DB-25 Connector)

Pin# Signal Signal Direction

3 Receive From 2720
2 Transmit Data To 2720
7 Ground

Pin# Signal Signal Direction

2 Receive From 2720
3 Transmit Data To 2720
5 Ground

Signal

TRS Jack (RS-232 Control Port)

Signal Direction

RS-232 Control Port (Signals at DB-9 Connecter)

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NOTES

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Copyright © 2001, 2007

Patton Electronics Company

All Rights Reserved