VARIABLE LOOP LENGTH COMPENSATED OPTOCOUPLED CIRCUIT

摘要

A gain and frequency compensated optocoupled circuit is disclosed for use with a telephone transmission line having variable loop lengths. A DC component of the input signal is provided to the input of an optocoupled circuit. Loop length losses, as well as optocoupled gain variations, are adjusted on the output side of the circuit by comparing the DC optocoupled voltage level with a DC reference level and adjusting the AC gain. Frequency response, which is also a function of loop length, is corrected by using the DC input voltage to generate an effective loop length dependent capacitor for further controlling the output signal level.