Key telephone system with distributed control

A system for accessing a plurality of main exchange lines (C01, C02, C03) by a plurality of stations and for exchanging signals between the stations. Each station is provided with a self-sufficient microprocessor (10) which controls all the functions of the station. The microprocessors exchange control signals to indicate the status of each station and each line. A common intercom line is provided for both audio signals and control signals. Each station is assigned a unique address so that each station is able to dial up another station for intercom communication by generating the proper control signals. Each station is also provided with a switch matrix (120) for selectively accessing any of the lines, line status indicating means (32, 34, 36) and line holding means (52. 54, 56) which is automatically released when any station accesses the held line.