D4 Digital Channel Bank Family: Digital Terminal Physical Design

D4 Digital Channel Bank Family: Digital Terminal Physical Design By W. G. A L B E R T , A. G. F A V A L E , J. R. H A L L , and D. H. K L O C K O W (Manuscript received August 26, 1981) This article describes the physical design of the D4 and related SLCTM-36 subscriber loop carrier system digital terminals. A detailed description of the bay, channel bank, and plug-in designs is also included, along with other very important considerations such as thermal design, manufacturability, and the effective use of hybrid integrated circuit technology. The D4 was designed as a system that was significantly smaller, used less power, and had a lower cost than previous digital terminals. These objectives were realized by using the latest technology and the optimal physical design format. Since these are relatively high-production terminals, the basic design has been aggressively reduced in cost and has proliferated with expanding D4 and SLC-96 subscriber loop carrier terminal capabilities, lightguide applications, and the use of the D4 hardware in other systems. I. INTRODUCTION In 1962 the D1 channel bank, the voice-frequency (VF) pulse code modulation (PCM) terminal for the T1 carrier system, was first introduced into Commercial Exchange Office service. The 11-foot 6-inch central office bay framework contained equipment for 72 voice channels (three 24-channel banks). Discrete, solid-state technology was used and the typical power consumption was about 7.5 watts per channel. In 1969 the D2 channel bank was introduced into service for Toll Office applications.