Transmission overload protection appts. - has protection compensating amplifier triggered by absolute value and by direction of overload measuring triggers

摘要

Circuit design for triggering an overload protection system in an amplifier. The protection circuit triggering is dependent upon the amplitude of an incoming interfering voltage, it is designed to operate quickly to insert an antiphase signal to reduce the level of the interference. The protection amplifier (1) inserts a compensatory signal onto the transmission line (3,5) by means of a transformer coupling (4). The protection amplifier (1) monitors the incoming signal (2) on a 'pilot' wire (3) and has associated circuitry (6,7,9) to monitor the absolute value and differential quotient direction of the interfering overload signal so that the logic circuit (7) operates a relay (10) to cause the protection amplifier (1) to insert its protection signal onto the line. A Schmitt trigger (9) is used to determine interfering overload direction and absolute valve.