ARM - Asynchronous Response Mode NDM - Normal Disconnected Mode NRM - Normal Response Mode HDLC - High-Level Data Link Control DM - Disconnected Mode RD - Request Disconnect SIM - Set Initialization Mode SNRME - Set Normal Response Mode Extended SARM - Set Asynchronous Response Mode UP - Unnumbered Poll UA - Unnumbered Acknowledgment SARME - Set Asynchronous Response Mode Extended