Reference Information 
  Modem Reference Information 
    Corporate Evaluator’s Guide  199 
Modem Reference Information 
If your computer has a modem port, you can customize the operation of the modem using 
AT commands and S-registers. You can do this from Modem (Windows 98) or Phone 
and Modem Options (Windows 2000 and XP) in Control Panel, from most 
communications software, or by using terminal mode in your software. See “To change 
your modem settings” on page 61. 
Note 
You should have a good understanding of modems and how they operate before you 
change default settings. 
This section contains summary information about AT commands, S-registers, and 
selected result codes for the built-in modem. Your computer has either a 3Com/US 
Robotics or Ambit (ESS) modem. To determine which brand is in your computer: 
•  Open Modems (Windows 98) or Phone and Modem Options (Windows 2000 or XP) 
in Control Panel. 
Modem Reference (Ambit) 
In the following AT command table, default settings are shown in bold. All listed AT 
commands except A/ must be preceded by “AT.” 
AT Commands (Ambit) 
Command Function (Ambit) 
A/  Re-execute command (not preceded by AT) 
A  Go off-hook and attempt to answer a call 
B0  Select V.22 connect @1200 bps 
B1  Select Bell 212A connect @1200 bps 
C1 Return OK message 
Dn Dial modifier 
E0  Turn off command echo 
E1  Turn on command echo 
H0  Initiate a hang-up sequence 
H1  If on-hook, go off-hook and enter command mode 
I0  Report product code 
I1  Report pre-computed checksum 
I2  Report “OK” if the calculated checksum equals the prestored checksum or if the prestored checksum value 
is FFh 
I3  Report firmware revision, model, and interface type 
I4  Report response programmed by OEM  
I5  Report the country code parameter