This paper discusses in broad terms the design of a radically new family of multiplex terminals, designated the L multiplex, designed to work with any of several broadband transmission facilities. The relevant historical background of multiplex terminals is covered and design objectives for the new equipment are outlined. The new multiplex takes advantage of advances in the state of the art to reduce the size of equipment and increase reliability, while it retains the proven advantages of older equipment. Other advantages of the new multiplex include in‐service maintenance, decentralized carrier supplies, and increased flexibility. The latter permits its use with as few as 60 or as many as 1860 voice channels and also adapts it for use with wideband data service. Compatibility with older multiplex equipment was maintained where possible, but in order to meet future demands for broadband service, it was decided to modify older equipment rather than compromise the design of the new to maintain compatibility.

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This article presents a brief historical background to the A‐series of terminal units, used extensively in long‐haul and short‐haul transmission facilities to provide the first step of modulation from voice to carrier and the final step of demodulation from carrier to voice. Most of the paper is devoted to a description of the latest unit of this series — the A5 channel bank, which through the use of transistors and other modern components achieves significant improvements in size, power requirements and operating characteristics.

A paper by Leconte, Penick, Schramm and Wier discusses the system aspects of 8‐kc program circuits over carrier facilities and outlines the functions of several filters and networks. This paper describes in detail two of the filters and one network. These are: The channel selecting crystal band pass filter used at program terminals of all broad‐band carrier systems, The band elimination filter which blocks the program at branching points on type K carrier systems, The network used at branching points on type K carrier systems to simulate the phase shift of the band elimination filter.

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