Automatic telegraph switching system plan 55-A

The 200,000-mile private-wire network of the United States Air Force includes five Plan 51 switching centers in the United States, leased from The Western Union Telegraph Company. These centers are interconnected by trunk lines and each center has lines radiating to tributary stations in its area. Gateway centers near the Atlantic and Pacific coasts extend the network over radio channels to numerous Air Force installations overseas. This network has been in operation since February 1951. Satisfactory experience in operating this network, with its push-button-operated Plan 51 switching centers, has led the Air Force to request Western Union to engineer a fully automatic switching system for world-wide use. It is expected that automatic switching will increase the speed and efficiency of message handling and result in considerable reduction in operating labor. It will also provide for additional circuit capacity.