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The switched services network (SSN) is a new private line telephone service to provide customer dialed connections between PBX's at widely separated and scattered locations. This service differs from the presently used tandem tie line switching in that the network switching will be accomplished by 4-wire and 2-wire common control switching machines strategically located in telephone central offices throughout the country. This paper will describe the design of these networks and discuss the transmission objectives which have been developed to obtain a high degree of customer satisfaction on calls over the networks. As in any telephone transmission design problem, the major considerations are overall loss, echo, stability, noise, and the lossfrequency characteristics. Impulse noise and envelope delay characteristics are important considerations especially when data is to be transmitted over the network.