Abstract: A key telephone system has a plurality of telephone sets, each set having a hold button for temporarily holding a central office ("CO") line. A plurality of cell park lamps temporarily indicate which of the CO lines is being held. A plurality of call park buttons are individually associated with the call park lamps. An outgoing call button is used for seizing an idle one of the CO lines when an outgoing call is to be initiated. An answer button is used for seizing one of the CO lines over which an incoming call is being received. At least one external indicator indicates the various states (busy, idle, holding) of each of the CO lines. A central unit has a hold control circuit for indicating with the call park lamps when the CO line is being held responsive to an operation of either the hold button or a call park button.

Abstract: A key telephone system includes among other things a central switching network comprises of a main switch matrix including main talking paths and trunk paths, an auxiliary switch matrix including auxiliary talking paths and a coupling matrix between the main and auxiliary switch matrices and in which system each of the telephone station sets can talk through a plurality of talking paths, concurrently, and is capable of talking back hand-free.