Protective circuit for compass repeater amplifier systems

In a step-by-step angle data repeater system including transmitter means having plural output means providing phase-displaced multiple-wire step data voltages indicative of angle, cooperating step-by-step receiver means for repeating said angle and having corresponding plural input means, and plural data processing channels for coupling said respective plural output means to corresponding ones of said plural input means, the improvement wherein each said data processing channel comprises:

• trigger circuit means responsive to the presence of a high or a low output voltage level at a first of said plural output means,
• first diode means coupled in series with the output of said trigger circuit means,
• amplifier means coupled to said first diode means for supplying corresponding high or low excitation currents to a first of said plural output means and having current return means in common with said trigger circuit means,
• impedance means,
• second diode means having a gate control electrode,
• said impedance means and said second diode means being coupled in series relation between said first of said input means and said current return means,
• sensor impedance means sensing the amplitude of said excitation current for developing a corresponding sensor voltage thereacross, and
• network means coupling said sensor voltage to said gate control electrode whereby, only in the presence of said high excitation current and of a fault event causing said sensor voltage to increase above a predetermined level, said second diode latches in its conducting state, latching said amplifier means in its non-conducting state and protecting said amplifier means from destruction because of said fault event.