Transistors and their circuits in the 4A toll crossbar switching system

NATION-WIDE dialing is one of the more recent advances in the telephone art and has been the subject of papers presented before the AIEE.1 The heart of nation-wide dialing is the new no. 4A toll crossbar switching system. It is this system which, at the various control switching points, receives the digits dialed by the toll operators or by the subscribers. It then automatically determines the routing of the call to any destination in the United States, as well as in Canada, and proceeds to establish the connection to succeeding control switching points or to the local office. In this system it is necessary to translate the digits received into information as to the location of trunks on the switches, the kind of outpulsing required, the number of digits to send forward, and other such instructions.