Abstract: Apparatus is disclosed for incorporation into a key telephone system control unit, in at least one station port, for operating an at least one key type set and an at least one tip and ring device simultaneously bridged onto the same station port without the use of any special service circuits or adaptors. The ability to signal alerting indepenedntly via ringing signal on a TR-pair, via messages indicating alerting transmitted on a service pair for a key set or via both techniques simultaneously is also disclosed. Further, the alerting ability disclosed in combination with control by a key system controller of the access of a key set to voiceband communications over the TR-pair allows for incorporation of additional features into a key telephone system.