The Transistorized A5 Channel Bank for Broadband Systems

All of the long-haul, broadband transmission facilities of the Bell System, and many of the short-haul microwave radio systems, employ a common unit in their terminal multiplexes. This is the A type channel bank which provides the first step of modulation from voice to carrier spectrum and the reverse function of demodulation. From its inception over twenty-five years ago, the channel bank has undergone a number of size reductions primarily utilizing new types of crystal filters. This paper describes a radically new version, the A5 Channel Bank, with a detailed discussion of the new circuit feature -- the transistorized voice-frequency amplifier.