D4 Digital Channel Bank Family: The SLC-96 System

The subscriber loop is generally represented by pairs of metallic conductors that connect the customer's premises to the telephone network through a central office serving a locality. As low-cost electronic technologies continue to emerge, the subscriber loop, which was previously entirely metallic, is now being viewed as a potentially large market for the application of these technologies. 1 The electronic systems that have evolved to reduce the cost of growth in the loop plant are called pair gain systems. Most recently, the digital carrier-type pahgain systems appear to be well suited to growth of the network because of their high pair gain ratios realized by multiplexing with optional concentration and for their excellent signal quality resulting from digital transmission. The digital subscriber carrier system is being used in increasing numbers today in the Bell System to bring toll-quality channels to customers in both suburban and rural areas. The SLC-96 system is a new, versatile pair gain system that provides an economic means of linking subscriber lines to the central office.2'3 Like its predecessors, the SLC-96 system brings electronic technology to the loop plant, and in addition, the system may be used with the D4 channel bank to provide a new synergy between trunk and loop applications of digital carrier. Representing a significant step toward the Bell System's digital network of the future, the SLC-96 system can handle the broad spectrum of telecommunications services needed to meet today's widely varying requirements for both voice message and special communication services.