Telephone switching system with switched line circuits

摘要

An analog switch matrix provides limited connectability between a plurality of n telephone line appearances and a lesser plurality of m line interface circuits each connected with a communication path in a telephone system. The analog switch matrix includes n groups of 3 crosspoints each being operable to connect and disconnect a one of the n telephone line appearances at any of 3 line interface circuits, each of which is connectable to more than three of the line appearances. A switch matrix controller directs switching operations of the analog switch matrix in response to transitions to OFF HOOK states having been sensed at line appearances and in concert with the call controller in the telephone switching system. In a telephone system with a concentration ratio of 4:1 the grade of service is maintained by performance of a call transfer between ones of line interface circuits at any time during a call progress.