Dual Voltage Operation of Relays and Crossbar Switches

Making a connection from a customer's telephone to any of the other fifty million telephones in the United States requires a large and complex data processing or switching system. The equipment for this switching system is located in thousands of telephone central offices throughout the country. The equipment in a modern telephone central office may he listed within one of two catagories, the equipment which provides the "talking" or transmission connections through the office, and the control equipment which selects and controls these connections for the talking transmission facilities. Telephone switching offices in which the control equipment has been centralized are labeled "common" control switching offices since the centralized control equipment is available and used "in common" by all of the customers of the office. In these common cont rol switching offices information which is received from the calling customer is stored in "memory-mechanisms". Other memory devices store information about the switching network which is 1225