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Late in 1962 Bell Telephone Laboratories began the development of a 4-wire version of the No.1 ESS for government and military applications. An electronic stored program system was requested by the government to meet the growing needs of defense communication. There are now thirteen 4-wire No.1 ESSs in the government's AUTOVON network, in addition to 23 No. 5 crossbar offices, most placed in service prior to 1966. By 1969 it is anticipated that more than 50 Bell System offices will be in operation throughout the United States. By this time the crossbar machines will have started to be replaced by ESSs, as shown in Fig. 2. Additional electronic offices, overseas as well as in the United States and Canada, are being planned for AUTOVON by non-Bell System companies. Before 1970 a global defense communication network of ESSs should be realized. Early field experience with the No. 1 ESS, both 2- and 4- wire, has been satisfactory. New offices endowed with new service features and improved maintenance capabilities are being introduced at a growing rate. About 100 No. 1 ESSs are now in various stages of manufacture and installation or in field operation. The ability of this design to provide continuous, high-quality service seems assured.