TECHNICAL QUICK REFERENCE
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This section includes information about:
• Lights (external modems only)................................................................2
• Typing Commands.................................................................................4
• Basic Data Commands..........................................................................5
• Extended Data Commands...................................................................13
• DIP Switches......................................................................................20
• S-Registers.........................................................................................22
• Fax Commands...................................................................................33
• The Serial Interface (cable information)................................................37
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Lights (External Modems Only)
Front-of-the-Case Lights (on All Non-Voice Externals and Some Voice Externals)
Symbol Meaning Status
AA............Auto Answer Answer mode: ON when register S0 is set to 1 or higher (Auto Answer),
and when answering a call; OFF when modem originates a call. Light
flashes when there is an incoming call.
CD.............Carrier Detect ON if modem receives a valid data signal (carrier) from a remote modem,
indicating that data transmission is possible. Always ON if CD override is
ON (&C0).
RD.............Received Data Flashes when modem sends result codes or passes received data bits from
remote.
SD..............Send Data Flashes when computer sends a data bit to modem.
TR..............Data Terminal Ready ON if modem receives a DTR signal from computer. Always ON (modem
ignores DTR) if the DTR override is ON (&D0).
CS..............Clear to Send ON until modem lowers CTS when Transmit Data hardware flow control is
enabled (&H1, &H3).
ARQ/ Error Control/
FAX..........Fax Operations Data Mode: Automatic Repeat Request. ON if modem is set to &M4 or &M5
and successfully establishes an error control connection. Flashes when
modem retransmits data to remote modem. Fax Mode: Flashes to indicate fax
mode.
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Top-of-the-Case Lights (on Some Voice Externals)
Light What It Means When Lit
POWER................The modem is turned on.
SEND...................The computer is sending a data bit to the modem.
RECEIVE .............The modem is sending result codes or passing received data bits from the remote.
ONLINE...............The modem is online. (NOTE: This light blinks when the mute feature is being
used.)
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Typing Commands
• Type commands in either upper or lower case, not a combination. Use the
Backspace key to delete errors. (You cannot delete the original AT command since
it is stored in the modem buffer.)
• If a command has numeric options and you don’t include a number, zero is
assumed. For example, if you type ATB, the command ATB0 is assumed.
• Every command except A/, +++, and A> must begin with the AT prefix and be entered
by pressing ENTER.
• The maximum command length is 58 characters. The modem doesn’t count the AT prefix,
carriage returns, or spaces.
NOTE: All defaults are based on the &F1Hardware Flow Control template
loaded in NVRAM when the modem is shipped. Defaults are listed in italics.
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Basic Data Commands
<control key>S
Stop or restart help screens.
<control key>C
or
<control key>K
Stop help screens.
$ Use in conjunction with D, S,
or & commands (or just AT)
to display a basic command
list; online help.
A Manual Answer: goes off hook
in answer mode. Pressing any
key aborts the operations.
A/ Re-executes the last issued
command. Used mainly to
redial. Does not require the
AT prefix or a Carriage
Return.
A> Re-executes the last issued
command continuously, until
the user intervenes or the
command is executed. forever.
Does not require the
AT prefix or a Carriage
Return.
Any key Aborts off-hook dial/answer
operation and hangs up.
AT Required command prefix, except
with A/, +++, and A>. Use alone to
test for OK result code.
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Bn U.S./ITU-T answer
sequence.
B0 ITU-T answer
sequence
B1 U.S. answer tone
Dn Dials the specified phone
number. Includes the
following:
0-9 Numeric digits
#, * Extended touch-tone
pad tones
L Dials the last dialed number.
P Pulse (rotary) dial
R Originates call using answer
(reverse) frequencies.
Sn Dials the phone number string
stored in NVRAM at position
n (n = 0−3). Phone numbers
are stored with the &Zn=s
command.
T Tone dial
, (Comma) Pause, See S8
definition; which it’s
linked to.
; (Semicolon) Return to
Command mode after dialing.
“ Dials the letters that follow (in
an alphabetical phone
number).
! (Exclamation point) Flashes
the switch hook.
/ Delays for 125 ms. before
proceeding with dial string.
W Wait for second dial tone (X2
or X4); linked to S6 register.
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Dn (cont.)
@ Dials, waits for quiet answer,
and continues (X3 or higher).
$ Displays a list of Dial
commands.
En Sets local echo.
E0 Echo OFF
E1 Modem displays
keyboard commands
Fn Sets online local echo of
transmitted data ON/OFF.
F0 Local echo ON.
Modem sends a copy
of data it sends to the
remote system to your
screen.
F1 Local echo OFF. Receiving
system may send a remote
echo of data it receives.
Hn Controls ON/OFF hook.
H0 Hangs up (goes on hook).
H1 Goes off hook.
In Displays the following information.
I0 Four-digit product code
I1 Results of ROM checksum
I2 Results of RAM checksum
I3 Product type
I4 Current modem settings
I5 Nonvolatile memory
(NVRAM) settings
I6 Link diagnostics
I7 Product configuration
I9 Plug and Play information
I11 Extended link diagnostics
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Ln Controls speaker volume
(internals only).
L0 Low volume
L1 Low volume
L2 Medium volume
L3 High volume
Mn Operates speaker.
M0 Speaker always OFF.
M1 Speaker ON until
CONNECT.
M2 Speaker always ON.
M3 Speaker ON after dial,
until CONNECT.
On Returns online.
O0 Returns online.
O1 Returns online and
retrains.
P Sets pulse dial (for phone
lines that don’t support
touch-tone dialing).
Qn Displays/suppresses result
codes.
Q0 Displays result codes.
Q1 Quiet mode; no result
codes.
Q2 Displays result codes
only in Originate
mode.
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Sr.b=nSets bit .b of register r to n
(0/OFF or 1/ON).
Sr=n Sets register r to n.
Sr? Displays contents of
S-Register r.
S$ Displays a list of the S-
Registers.
T Sets tone dial.
Vn Displays verbal/numeric
result codes.
V0 Numeric codes
V1 Verbal codes
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Xn Sets result code displayed. Default is X4.
Result Codes X0 X1 X2 X3 X4
0/OK • • • • •
1/CONNECT • • • • •
2/RING • • • • •
3/NO CARRIER • • • • •
4/ERROR • • • • •
5/CONNECT 1200 • • • •
6/NO DIAL TONE • •
7/BUSY • •
8/NO ANSWER* • •
9/Reserved
10/CONNECT 2400 • • • •
11/RINGING •
13/CONNECT 9600 • • • •
18/CONNECT 4800 • • • •
20/CONNECT 7200 • • • •
21/CONNECT 12000 • • • •
25/CONNECT 14400 • • • •
43/CONNECT 16800 • • • •
85/CONNECT 19200 • • • •
91/CONNECT 21600 • • • •
99/CONNECT 24000 • • • •
103/CONNECT 26400 • • • •
107/CONNECT 28800 • • • •
151/CONNECT 31200 • • • •
155/CONNECT 33600 • • • •
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Xn Result Codes (cont.) X0 X1 X2 X3 X4
256/CONNECT 28000 • • • •
260/CONNECT 29333 • • • •
264/CONNECT 30666 • • • •
268/CONNECT 32000 • • • •
180/CONNECT 33333 • • • •
272/CONNECT 34666 • • • •
276/CONNECT 36000 • • • •
184/CONNECT 37333 • • • •
280/CONNECT 38666 • • • •
284/CONNECT 40000 • • • •
188/CONNECT 41333 • • • •
192/CONNECT 42666 • • • •
196/CONNECT 44000 • • • •
200/CONNECT 45333 • • • •
204/CONNECT 46666 • • • •
208/CONNECT 48000 • • • •
212/CONNECT 49333 • • • •
216/CONNECT 50666 • • • •
220/CONNECT 52000 • • • •
224/CONNECT 53333 • • • •
228/CONNECT 54666 • • • •
232/CONNECT 56000 • • • •
236/CONNECT 57333 • • • •
Adaptive Dialing • • •
Wait for 2nd Dial Tone (W) • •
Wait for Answer (@) • •
Fast Dial • •
*Requires @ in dial string; replaces NO CARRIER
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Yn Selects power-on/reset
default configuration.
Y0 Use profile 0 setting
in NVRAM
Y1 Use profile 1 setting in
NVRAM
Y2 Use factory
configuration 0.
Y3 Use factory
configuration 1.
Y4 Use factory
configuration 2
Z Resets modem.
Z0 Resets modem to
NVRAM profile
selected by Y
command or dip 7.
Z1 Resets modem to
NVRAM profile 0
Z2 Resets modem to
NVRAM profile 1
Z3 Resets modem to
factory default profile
0 (&F0)
Z4 Resets modem to
factory default profile
1 (&F1)
Z5 Resets modem to
factory default profile
2 (&F2)
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Extended Data Commands
&$ Displays a list of ampersand (&)
commands.
&An Enables/disables additional result
code subsets (see Xn).
&A0 ARQ result codes disabled
&A1 ARQ result codes enabled
&A2 V.32 modulation indicator added
&A3 Protocol indicators added
LAPM/MNP/NONE (error
control) and V42bis/MNP5
(data compression)
&Bn Manages modem’s serial port rate.
&B0 Variable, follows connection
rate
&B1 Fixed serial port rate
&B2 Fixed in ARQ mode, variable in
non-ARQ mode
&Cn Controls Carrier Detect (CD)
signal.
&C0 CD override
&C1 Normal CD operations
&Dn Controls Data Terminal Ready
(DTR) operations.
&D0 DTR override
&D1 DTR toggle causes online
Command mode
&D2 Normal DTR operations
&D3 Resets on receipt of DTR
&Fn Loads a read-only (non-programmable)
factory configuration.
&F0 Generic template
&F1 Hardware flow control
template
&F2 Software flow control template
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&Gn Sets Guard Tone.
&G0 No guard tone, U.S. and
Canada
&G1 550 Hz guard tone, some
European countries, requires
B0 setting.
&G2 1800 Hz guard tone, U.K.,
requires B0 setting.
&Hn Sets Transmit Data (TD) flow
control (see also &Rn).
&H0 Flow control disabled
&H1 Hardware flow control,
Clear to Send (CTS)
&H2 Software flow control,
XON/XOFF
&H3 Hardware and software flow
control
&In Sets Receive Data (RD) software
flow control (see also &Rn).
&I0 Software flow control
disabled
&I1 XON/XOFF signals to your
modem and remote system
&I2 XON/XOFF signals to your
modem only
&Kn Enables/disables data compression.
&K0 Data compression disabled
&K1 Auto enable/disable
&K2 Data compression enabled
&K3 MNP5 compression
disabled
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&Mn Sets Error Control (ARQ) for
connections at 1200 bps and higher.
&M0 Normal mode, error control
disabled
&M1 Reserved
&M2 Reserved
&M3 Reserved
&M4 Normal/ARQ
&M5 ARQ mode
&Nn Sets connect speed. If connection
cannot be made at this speed, the
modem will hang up. When used in
conjunction with &Un and &Un is
greater than 0, &Nn sets the
ceiling connect speed. &Un sets
the floor connect speed (See also
the table in the &Un section.)
&N0 Connection speed is
determined by
the remote modem.
&N1 300 bps
&N2 1200 bps
&N3 2400 bps
&N4 4800 bps
&N5 7200 bps
&N6 9600 bps
&N7 12,000 bps
&N8 14,400 bps
&N9 16,800 bps
&N10 19,200 bps
&N11 21,600 bps
&N12 24,000 bps
&N13 26,400 bps
&N14 28,800 bps
&N15 31,200 bps
&N16 33,600 bps
&N17 28,000 bps
&N18 29,333 bps
&N19 30,666 bps
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&N20 32,000 bps
&N21 33,333 bps
&N22 34,666 bps
&N23 36,000 bps
&N24 37,333 bps
&N25 38,666 bps
&N26 40,000 bps
&N27 41,333 bps
&N28 42,666 bps
&N29 44,000 bps
&N30 45,333 bps
&N31 46,666 bps
&N32 48,000 bps
&N33 49,333 bps
&N34 50,666 bps
&N35 52,000 bps
&N36 53,333 bps
&N37 54,666 bps
&N38 56,000 bps
&N39 57,333 bps
&Pn Sets pulse (rotary) dial make/break
ratio.
&P0 U.S./Canada ratio, 39%/61%
&P1 U.K. ratio, 33%/67%
&Rn Sets Receive Data (RD) hardware
flow control, Request to Send
(RTS) (see also &Hn).
&R0 Reserved
&R1 Modem ignores RTS
&R2 Received Data to computer
only on RTS
&Sn Controls Data Set Ready (DSR)
operations.
&S0 DSR override; always ON
&S1 Modem controls DSR
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&Tn Begins test modes.
&T0 Ends testing
&T1 Analog Loopback
&T2 Reserved
&T3 Local Digital Loopback
&T4 Enables Remote Digital
Loopback
&T5 Prohibits Remote
Digital Loopback
&T6 Initiates Remote Digital
Loopback
&T7 Remote Digital with
self-test and error
detector
&T8 Analog Loopback with
self-test and error
detector
&Un Sets floor connect speed when set
above 0. If the connection cannot
be established above this speed,
the modem will hang up. When
&Un is used in conjunction with
&Nn and &Nn is greater than 0,
&Nn is the ceiling connect speed.
$N=0 &N>0
&U=0 Connects at Connects at
best possible speed defined
by your modem between &Nn
and the remote If the
modem. Connection
NOTE: These cannot be
factory default made above
settings should this speed the
be sufficient modem will
for most users. hang
&U>0 Connects at Connects at any
any speed speed faster than
between &Nn the value of
and &Un. &Un.
&Un speeds are listed on
the next page.
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&U0 No restrictions on the minimum
speed for the connection.
&U1 300 bps
&U2 1200 bps
&U3 2400 bps
&U4 4800 bps
&U5 7200 bps
&U6 9600 bps
&U7 12,000 bps
&U8 14,400 bps
&U9 16,800 bps
&U10 19,200 bps
&U11 21,600 bps
&U12 24,000 bps
&U13 26,400 bps
&U14 28,800 bps
&U15 31,200 bps
&U16 33,600 bps
&U17 28000 bps
&U18 29333 bps
&U19 30666 bps
&U20 32000 bps
&U21 33,333 bps
&U22 34666 bps
&U23 36000 bps
&U24 37,333 bps
&U25 38666 bps
&U26 40000 bps
&U27 41,333 bps
&U28 42,666 bps
&U29 44,000 bps
&U30 45,333 bps
&U31 46666 bps
&U32 48000 bps
&U33 49333 bps
&U34 50666 bps
&U35 52000 bps
&U36 53333 bps
&U37 54666 bps
&U38 56000 bps
&U39 57333 bps
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&Wn Writes current configuration to
NVRAM templates.
&W0 Modifies the NVRAM 0
template (Y0)
&W1 Modifies the NVRAM 1
template (Y1)
&Yn Sets break handling.
&Y0 Destructive, but doesn’t send
break
&Y1 Destructive, expedited
&Y2 Nondestructive, expedited
&Y3 Nondestructive, unexpedited
&Zn=s Writes phone number string s
to NVRAM at position n (n
= 0−3).
&Zn=L Writes last executed dial
string to NVRAM at position
n (n = 0−3).
&Zn? Displays the phone number stored at
position n (n = 0−3).
&ZL? Displays the last executed dial string.
#CID=n Controls Caller ID feature.
#CID=0 Caller ID disabled.
#CID=1 Caller ID enabled
with formatted
information.
#CID=2 Caller ID enabled
with unformatted
information.
+++ Escapes to online-command mode.
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DIP Switches (External Modems with DIP Switches Only)
Note: If a DIP switch is on, it is down. If a DIP switch is off, it is up. Defaults are in italics.
Factory
Switch Setting Function
1 OFF Data Terminal Ready (DTR) Override
OFF Normal DTR operations: computer must provide DTR signal for the
modem to accept commands; dropping DTR terminates a call
ON Modem ignores DTR (Override)
2 OFF Verbal/Numeric Result Codes
OFF Verbal (word) results
ON Numeric results
3 ON Result Code Display
OFF Suppresses result codes
ON Enables result codes
4 OFF Command Mode Local Echo Suppression
OFF Displays keyboard commands
ON Suppresses echo
5 ON Auto Answer Suppression
OFF Modem answers on first ring, or higher if specified in NVRAM
ON Disables auto answer
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Factory
Switch Setting Function
6 OFF Carrier Detect (CD) Override
OFF Modem sends CD signal when it connects with another modem, drops
CD on disconnect
ON CD always ON (Override)
7 OFF Power-on and ATZ Reset Software Defaults
OFF Loads Y0-Y4 configuration from user-defined nonvolatile memory
(NVRAM)
ON Loads &F0Generic template from read only memory (ROM)
8 ON AT Command Set Recognition
OFF Disables command recognition (Dumb Mode)
ON Enables recognition (Smart mode)
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S-Registers
To change a setting, use the ATSr=n command, where r is the register and n is a decimal
value from 0 − 255 (unless otherwise indicated).
Register Default Function
S0 0 Sets the number of rings on which to answer in Auto Answer mode. When set to 0,
Auto Answer is disabled.
S1 0 Counts and stores the number of rings from an incoming call. (S0 must be greater
than 0.)
S2 43 Stores the ASCII decimal code for the escape code character. Default character is
+. A value of 128 – 255 disables the escape code.
S3 13 Stores the ASCII code for the Carriage Return character. Valid range is 0 –
127.
S4 10 Stores the ASCII decimal code for the Line Feed character. Valid range is 0 –
127.
S5 8 Stores the ASCII decimal code for the Backspace character. A value of 128
−
255 disables the Backspace key’s delete function.
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Register Default Function
S6 2 Sets the number of seconds the modem waits before dialing. If Xn is set to X2 or
X4, this is the time-out length if there isn't a dial tone.
S7 60 Sets the number of seconds the modem waits for a carrier. May be set for much
longer duration if, for example, the modem is originating an international connection.
S8 2 Sets the duration, in seconds, for the pause (,) option in the Dial command.
S9 6 Sets the required duration, in tenths of a second, of the remote modem’s carrier
signal before recognition by the U.S. Robotics modem.
S10 14 Sets the duration, in tenths of a second, that the modem waits to hang up after loss
of carrier. This guard time allows the modem to distinguish between a line
disturbance from a true disconnect (hang up) by the remote modem.
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Register Default Function
S10 (cont.) Note: If you set S10 = 255, the modem will not hang up when carrier is lost.
Dropping DTR hangs up the modem.
S11 70 Sets the duration and spacing, in milliseconds, for tone dialing.
S12 50 Sets the duration, in fiftieths of a second, of the guard time for the escape code
sequence (+++).
S13 0 Bit-mapped register. Select the bit(s) you want on and set S13 to the total of the
values in the Value column. For example, ATS13 = 17 enables bit 0 (value is 1) and
bit 4 (value is 16).
Bit Value Result
0 1 Reset when DTR drops.
1 2 Reset non-MNP transmit buffer from 1.5K to 128
bytes.*
2 4 Set backspace key to delete.
3 8 On DTR signal, autodial the number stored in
NVRAM at position 0.
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Register Default Function
S13 (cont.) Bit Value Result
4 16 At power on/reset, autodial the number stored in
NVRAM at position 0.
5 32 Reserved
6 64 Disable quick retrains.
7 128 Disconnect on escape code.
*
The 1.5K-byte non-ARQ buffer allows data transfer with Xmodem- and Ymodem-type file transfer
protocols without using flow control.
The 128-byte option lets remote users with slower modems keep data you’re sending from scrolling
off their screens. When remote users send your computer an XOFF (Ctrl-S) and you stop transmitting,
the data in transit from your modem’s buffer doesn’t exceed the size of their screen.
This is also very helpful in situations when a remote modem/printer application is losing characters.
S14 0 Reserved
S15 0 Bit-mapped register setup. To set the register, see instructions for S13.
Bit Value Result
0 1 Disable ARQ/MNP for V.22.
1 2 Disable ARQ/MNP for V.22bis.
2 4 Disable ARQ/MNP V.32/V.32bis/V.32terbo.
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Register Default Function
S15 (cont.) Bit Value Result
3 8 Disable MNP handshake.
4 16 Disable MNP level 4.
5 32 Disable MNP level 3.
6 64 MNP incompatibility.
7 128 Disable V.42 operation.
To disable V.42 detect phase, select the total of the values for bits 3
and 7 (in other words S15 = 136 [the sum of values 8 and 128])
S16 0 Reserved
S17 0 Reserved
S18 0 Test timer for &T loopback testing. Sets the time in seconds of testing before the
modem automatically times out and terminates the test. When set to 0, the timer is
disabled. Valid range is 1-255.
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Register Default Function
S19 0 Sets the duration, in minutes, for the inactivity timer. The timer activates when there
is no data activity on the phone line; at time-out the modem hangs up. S19 = 0
disables the timer.
S20 0 Reserved
S21 10 Sets the length, in 10-millisecond units, of breaks sent from the modem to the
computer; applies to MNP or V.42 mode only.
S22 17 Stores the ASCII decimal code for the XON character.
S23 19 Stores the ASCII decimal code for the XOFF character.
S24 0 Reserved
S25 20 Sets the duration, in hundredths of a second, that DTR must be dropped so that the
modem doesn’t interpret a random glitch as a DTR loss. (Most users will want to
use the default; this register is useful for setting compatibility with older systems
running under older operating software.)
S26 0 Reserved
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Register Default Function
S27 0 Bit-mapped register setup. To set the register, see instructions for S13.
Bit Value Result
0 1 Enables ITU-T V.21 modulation at 300 bps for
overseas calls; in V.21 mode, the modem answers
both overseas and domestic (U.S. and Canada) calls,
but only originates V.21 calls. (Default Bell 103)
1 2 Enables unencoded (non-trellis coded) modulation in
V.32 mode.
2 4 Disables V.32 modulation.
3 8 Disables 2100 Hz answer tone to allow two V.42
modems to connect faster.
4 16 Enables V.23 fallback mode.
5 32 Disables V.32bis mode.
6 64 Disable V.42 selective reject.
7 128 Software compatibility mode. This setting disables the
codes and displays the 9600 code instead. The actual
rate of the call can be viewed on the ATI6 screen.
Used for unusual software incompatibilities. Some
software may not accept 7200, 12,000, and 14,400
bps or greater result codes.
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Register Default Function
S28 0 Eliminates the V.32 answer tones for a faster connection.
8 Default item, all times are in tenths of seconds.
255 Disables all connections except V.32 at 9600 bps.
S29 20 Sets the duration, in tenths of a second, of the V.21 answer mode fallback timer.
S30 0 Reserved
S31 128 Reserved
S32 2 Bit-mapped register setup. To set the register, see the instructions for S13.
Bit Value Result
0 1 V.8 Call Indicate enabled.
1 2 Enables V.8 mode.
2 4 Reserved.
3 8 Disable V.34 modulation.
4 16 Disable V.34+ modulation.
5 32 Disable x2 modulation.
6 64 Disable V.PCM modulation.
7 128 Reserved.
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Register Default Function
S33 0 Bit-mapped register setup. To set the register, see the instructions for S13.
Bit Value Result
0 1 Disable 2400 symbol rate.
1 2 Disable 2743 symbol rate.
2 4 Disable 2800 symbol rate.
3 8 Disable 3000 symbol rate.
4 16 Disable 3200 symbol rate.
5 32 Disable 3429 symbol rate.
6 64 Reserved
7 128 Disable shaping.
S34 0 Bit-mapped register setup. To set registers, see instructions for S13.
Bit Value Result
0 1 Disable 8S-2D trellis encoding.
1 2 Disable 16S-4D trellis encoding.
2 4 Disable 32S-2D trellis encoding.
3 8 Disable 64S-4D trellis encoding.
4 16 Disable non-linear coding.
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Register Default Function
S34 (cont.) Bit Value Result
5 32 Disable TX level deviation.
6 64 Disable Pre-emphasis.
7 128 Disable Pre-coding.
S35-S37 Reserved
S38 0 Sets an optional delay, in seconds, before a forced hang-up and clearing of the Transmit buffer
when DTR drops during an ARQ call. This allows time for a remote modem to acknowledge
receipt of all transmitted data before it is disconnected. The modem immediately hangs up
when DTR drops.
This option only applies to connections terminated by dropping DTR. If the modem receives
the ATH command, it ignores S38 and immediately hangs up.
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Register Default Function
S39-S40 Reserved
S41 0 Bit-mapped register setup. To set registers, see instructions for S13.
Bit Value Result
0 1 Distinctive ring enabled.
1 2 Speakerphone connect message override
(voice products only).
2 4 Reserved.
3 8 Message waiting (voice products only).
4 16 Reserved.
5 32 Reserved.
6 64 Reserved.
7 128 Reserved.
S42 0 Reserved
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Fax Commands
+FCLASS=n Sets the mode of operation.
FCLASS=0 Data mode
FCLASS=1 Group 3 Facsimile Service Class 1 mode
FCLASS? Displays the current FCLASS mode. (See mode descriptions
above.)
+FCLASS=? Displays the FCLASS mode options. (See mode descriptions
above.)
+FTS=n Stops the fax transmission. Then the modem waits for a specified
time before OK appears on screen. The pause is set in
10 millisecond intervals. n is the number of 10 millisecond
intervals that pass before OK appears. (n=0-255)
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+FRS=n Makes the modem wait for a specified length of silence before
sending OK to the screen. The pause is set in
10 millisecond intervals. n is the number of 10 millisecond
intervals that pass before OK appears. (n=0-255)
Note: This command terminates with OK when either the
specified amount of silence is detected or when the user types
anything (which is ignored).
+FTM=n Transmits data using the modulation specified by n.
(n = 3, 24, 48, 72, 96, 97, 98, 121, 122, 145, or 146)
Note: See the “Screen Messages” table at the end of this section
for an explanation of messages that appear in response
to this command.
+FRM=n Receives data using the modulation specified by n.
(n = 3, 24, 48, 72, 96, 97, 98, 121, 122, 145, or 146)
Note: See the “Screen Messages” table at the end of this section
for an explanation of messages that appear in response
to this command.
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+FTH=n Transmits data framed in the HDLC protocol using
the modulation specified by n.
(n = 3, 24, 48, 72, 96, 97, 98, 121, 122, 145, or 146)
Note: See the “Screen Messages” table at the end of this section
for an explanation of messages that appear in response
to this command.
+FRH=n Receives data framed in the HDLC protocol using
the modulation specified by n.
(n = 3, 24, 48, 72, 96, 97, 98, 121, 122, 145, or 146)
Note: See the “Screen Messages” table at the end of this section
for an explanation of messages that appear in response
to this command.
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Screen Messages
Displayed Displayed Description
as a number in words
0 OK The previous command has been processed
successfully.
1 CONNECT The modem has just connected to another modem.
2 RING Reports the receipt of a network altering ring.
3 NO CARRIER No carrier is being received from the modem.
4 ERROR The previous command line has not been recognized
or was completed abnormally.
5 NO DIAL (Optional) Dial tone was not received within
TONE the time-out period.
6 BUSY (Optional) A busy signal was deleted.
64 CONNECT/FAX (Optional) The modem has established a fax connection. This response
is used only when the fax mode is selected.
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37
The Serial Interface
The serial interface is a standard developed by the Electronic Industries Association
(EIA). It defines the signals and voltages used when data is exchanged between a
computer and a modem or serial printer.
The entire standard covers many more functions than are used in most data
communications applications. Data is transmitted between the devices over a shielded
serial cable with a 25-pin male (DB-25) connector to the modem and a 25-pin, 9pin, 8-pin, or custom-built connector to the computer.
FCC regulations require the use of a shielded cable when connecting a modem to a
computer to ensure minimal interference with radio and television.
Pin assignments are factory-set in the U.S. Robotics modem to match the standard
DB-25 assignments in the following table. DB-9 connectors for IBM/AT-compatible
computers should be wired at the computer end of the cable as shown in the DB-9
column.
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38
Serial Interface Pin Definitions
Signal Source
DB-25 DB-9 Circuit Function Computer/Modem
1 — AA Chassis Ground Both
2 3 BA Transmitted Data Computer
3 2 BB Received Data Modem
4 7 CA Request to Send Computer
5 8 CB Clear to Send Modem
6 6 CC Data Set Ready Modem
7 5 AB Signal Ground Both
8 1 CF Carrier Detect Modem
12 — SCF Speed Indicate Modem
20 4 CD Data Terminal Ready Computer
22 9 CE Ring Indicate Modem
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