User`s manual

U.S. Robotics I-modem Command Reference
Analog Synchronous Applications • Page 16-12
These are the extended result codes (X1) that replace CFI and INV.
LSN List of stored numbers
VAL Valid
CFAB Call aborted
CFCB Local I-modem busy
CFET Remote device busy
CFFC Forbidden call
CFNS Number not stored
CFNT Answer tone not detected
INVCU Command unknown
INVMS Message syntax error
INVPS Parameter syntax error
INVPV Parameter value error