AT commands and responses are active in command mode only; as determined by the state of the DSR line. Command mode behavior conforms to ANSI/TIA/EIA-602-1992 section 5, with the limitations stated below. The AT command set is a subset of the AT command set defined in ANSI/TIA/EIA-602 and in the CDPD System Specification Part 2014 Version 1.1, section 4.