Transistors in 4A toll crossbar switching

THE LATEST ADVANCE in the automatic handling of toll telephone calls is the 4A Toll Crossbar Switching System. The heart of this system is the card translator. In it is stored the necessary information to route a call to any one of the toll or local offices in the United States and Canada. Its operation is based on selecting a pattern of light beams corresponding to the routing information required. Determination of the routing information is made by detecting which light beams, called channels, are present during each translation.