The Equalizer Remote-Control System

The equalizer remote-control system has been developed and incorporated into the L-4 carrier system as part of an over-all plan for providing in-service equalization capability. Reference 2 describes the controllable transmission elements, which are step-adjustable equalizers with associated solid-state logic and memory circuits. The equalization control technique is based on measurements of the relative powers from test oscillators when they are successively and remotely connected to the inputs and outputs of the equalizers. Disparities in the relative received powers from different points reveal line misalignment and equalizer settings at the test-oscillator frequencies. The L-4 control system always consists of a sending and a receiving circuit located at an attended main station repeater and a loopback circuit at each of one or more remote main stations. The remote locations may be either attended or unattended. All commands orig953 954 TI-IE BELL SYSTEM TECHNICAL JOURNAL, APRIL 1969