A Remote Line Concentrator for a Time-Separation Switching Experiment

An earlier paper1 has described a research experiment on integrated communications using time-separation techniques. This experiment is called ESSEX (Experimental Solid State Exchange). The purpose of this paper is to discuss the environment and implementation of the remote line concentrators used in the experiment. ESSEX is an experiment designed to explore the possibilities of using digital systems in exchange area plant. Subscribers are connected to remote units that multiplex and convert analog signals to digital signals. Digital signals are transmitted and switched between remote units and are converted to analog form only at the units to which they are directed. The assemblages that provide the necessary switching and transmission functions for subscribers' lines are called concentrators-, those that provide the switching and transmission functions for trunks are called trunkors. Concentrators and trunkors form the basic building blocks of the system. A concentrator consists of two units called the remote line concentrator and the concentrator controller. The trunkor also has two parts, the trunkor unit and the trunkor controller. Since trunk groups ordinarily have high usage, the trunkor has no concentration, but otherwise it is identical to a concentrator. The remote line concentrator can serve a maximum of 255 subscribers. In a working system, however, traffic considerations would probably 31