Reference Information 
  Modem Reference Information 
    Corporate Evaluator’s Guide  207 
Command  Function (3Com/US Robotics) 
S$  Display the list of S-register settings 
Sr=n  Set S-Register “r” to “n” 
Sr?  Display the value of S-Register “r” 
V0  Display result codes in numeric form 
V1  Display result codes in verbose form (words)  
X0  Report basic call progress result codes, i.e., OK, CONNECT, RING, NO CARRIER, (also, for busy, if 
enabled, and dial tone not detected), NO ANSWER and ERROR  
X1  Report basic call progress result codes and the connect rates—OK, CONNECT, RING, NO CARRIER 
(also, for busy, if enabled, and dial tone not detected), NO ANSWER, CONNECT XXXX and ERROR 
X2  Report basic call progress result codes and the connect rates i.e., OK, CONNECT, RING, NO CARRIER 
(also, for busy, if enabled), NO DIAL TONE, NO ANSWER, CONNECT XXXX and ERROR 
X3  Report basic call progress result codes and connection rate i.e., OK, CONNECT, RING, NO CARRIER, NO 
ANSWER, CONNECT XXXX, BUSY and ERROR 
X4  Report all call progress result codes and connection rate i.e., OK, CONNECT, RING, NO CARRIER, NO 
ANSWER, CONNECT XXXX, BUSY, NO DIAL TONE and ERROR 
Y0  On the next reset, use &W0 settings  
Y1  On the next reset, use &W1 settings 
Y2  On the next reset use, &F0 settings 
Y3  On the next reset, use &F1 settings 
Y4  On the next reset, use &F2 settings  
Z0  Reset the modem according to the settings of ATY 
Z1  Reset the modem and use &W0 settings 
Z2  Reset the modem and use &W1 settings 
Z3  Reset the modem using &F0 settings and load factory default profile 1 
Z4  Reset the modem using &F1 settings and load factory default profile 0 
Z5  Reset the modem using &F2 settings and load factory default profile 2 
$  Display the list of AT commands  
&$  Display the list of ampersand commands  
&A0  Disable data compression result codes 
&A1  Enable data compression result codes 
&A2  Enable modulation result codes 
&A3  Enable data compression result codes and add V.42bis and MNP 5 protocol indicators 
&B0  Use a floating DTE speed 
&B1  Use a fixed DTE speed 
&B2  Use a fixed DTE speed when using data compression 
&C0  Carrier detect is always on 
&C1  Carrier detect is controlled by the modem. 
&D0 Ignore DTR 
&D1  Use online command mode 
&D2  DTE controls DTR 
&D3  DTE controls DTR and reset 
&F0  Set the factory profile that uses hardware (RTS/CTS) flow control (this is the active profile when the modem 
is shipped)  
&F1  Set the factory profile that uses hardware (RTS/CTS) flow control  
&F2  Set the factory profile that uses software (XON/XOFF) flow control 
&G0  No guard tone 
&G1  Use 550 Hz guard tone 
&G2  Use 1800 Hz guard tone 
&H0  Flow control for transmitted data - Disable flow control