Key telephone system

Claim 1

In a key telephone system comprising in combination a key service unit; a plurality of key telephone sets; at least one line circuit means for connecting said sets to an office line; at least one intercommunication line circuit means and intercommunication line circuit supervisory switching and control means, including register circuit means, for effecting interconnection of any one key telephone set in the system to another; and further wherein each of said key telephone sets incorporates a microphone and a loudspeaker; transmission network means; dial apparatus means; means for supplying outgoing voice representative signals generated by said microphone to said trasnsmission network means; means for supplying incoming voice representative signals, coupled to said transmission network, to said loudspeaker; and voice path switching circuit means for intercoupling said outgoing signal supplying means and said incoming signal supplying means to said transmission network and for maintaining said telephone set in its voice transmitting mode when said set is in the quiescent condition; the improvement wherein one of said key telephone sets serves all the other key telephone sets in the system as an operator attended station, said one key telephone set station additionally comprising circuit means, including a plurality of lamps, corresponding on a one-to-one basis to the plurality of other key telephone sets in the system, for indicating the status of each other key telephone set in the system; a like plurality of station selection key means and pairs of line conductor means, corresponding on a oneto-one basis to the plurality of other key telephone sets in the system, for interconnecting said operator attended station set to the plurality of other key telephone sets in the system; and means, responsive to the operation of a station selection key, a. for automatically holding a line circuit means operatively connected to said attended station set, b. for connecting the transmission network of said operator attended station set to the key telephone set corresponding to the operated selection key, over the corresponding pair of line conductors, and c. for supplying a calling signal to said last mentioned key telephone set.