Reference Information 
Modem Reference Information 
206  Corporate Evaluator’s Guide 
Modem Reference (3Com/US Robotics) 
In the following AT command table, default settings are shown in bold. All listed AT 
commands except +++, /, and A/ must be preceded by “AT.” 
AT Commands (3Com/US Robotics) 
Command  Function (3Com/US Robotics) 
+++  Escape to online command mode (not preceded by AT) 
/  Pause (not preceded by AT), 125 ms default 
A Answer manually 
A/  Repeat last command (not preceded by AT) 
D...  Dial a phone number and issue other optional commands: 0-9=Dial digit, T=Tone dial, P=Pulse dial, R=Call 
an originate-only modem, W=Wait for second dial tone (X2, X4), @=Wait for answer (X3, X4), 
(comma)=Pause in dialing, !=Flash switch hook, #=Auxiliary tone dial digit, *=Auxiliary tone dial digit, ;=Stay 
in command mode after dialing, $=Wait for calling card bong, &=Wait for calling card bong, “=Dial the letters 
that follow. 
D$  Display a list of dial commands  
DL  Redial last number 
DL?  Display last dialed number  
DSn  Dial stored number (n=0,1,2,3) 
E0  Turn command echo off 
E1  Turn command echo on 
F0  Turn online echo on 
F1  Turn online echo off 
H0  Hang up (go on-hook) 
H1  Pick up (go off-hook) 
I0  Display the 4-digit product code 
I1  Display the checksum 
I2  Display the RAM test results 
I3  Display the firmware version 
I4  Display the current modem settings 
I5  Display user profiles 
I7  Display the product configuration 
I8 Display blacklist screen 
I10  Display VXD configuration screen 
I11  Display V.34 link screen 
L0  Set modem speaker volume off 
L1  Set modem speaker volume on (low) 
L2  Set modem speaker volume on (medium) 
L3  Set modem speaker volume on (high) 
M0  The modem’s speaker is always off 
M1  The modem’s speaker is on until a connection is made 
M2  The modem’s speaker is always on 
M3  The modem’s speaker is off during dialing, and on after dialing until the connection is made 
O0  Return to online mode 
O1  Return to online mode and retrain (automatically return to the highest speed)