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The Bell system is planning to add a new circuit-switched digital capability (CSDC) to the telephone network. This new capability will provide for full duplex, circuit-switched, end-to-end synchronous 56 kbit/s digital connections. Using a combination of existing and new network elements, CSDC will allow present-day call setup methods and will support end-to-end digital data transmission in addition to voice transmission. Critical CSDC network elements are those associated with the loops between customers' premises and CSDC central offices. This paper provides an overview of the loop maintenance plan for CSDC, focusing on new automatic testing tools and test procedures. Also discussed are the network elements comprising CSDC (including loop configurations) and loop transmission performance objectives.