This part of IEC 60839 specifies the requirements for standard interfaces between the alarm system transceivers and transmission network where both form part of a dedicated channel alarm transmission system as defined in IEC 60839-5-4. This standard applies equally to the interface between an alarm system and the transmission where the alarm system transceiver functions are integrated into the control and indicating equipment (CIE). It also applies to the interface to the transmission network from the terminal receiver at the alarm receiving centre. This standard provides for a 1 200 Bd interface using the ITU-T Recommendation V.23 standard. This is required in order to ensure compatibility of equipment from different suppliers. The standard applies equally to the transmission of alarms and other messages to/from intrusion, fire, access control and social alarm systems, and to the transmission of information to/from other similar systems.