1000 B Pentaconta crossbar switching system

A description of the latent development of the Pentaconta system, the first design (called Pentaconta 500) being installed in 1954. The 1000 B version has been adopted for the Paris telephone network and is suitable for public exchanges of 1000 to 50 000 lines with a line unit capacity of 1000 subscribers. The switching function setting up of a local call, an outgoing call and the procedure for an incoming call are described with block diagrams. The function of the entraide or unit-overflow facility, one of the most important features of this system, is clearly explained. Photographs of various units and of the fault recording arrangement follow and finally layouts of racks and of typical 10 000-line exchange are given.