DEVICE FOR TRACKING TWO-WIRE AND FOUR-WIRE CHANNELS Russian patent published in 2002 - IPC

FIELD: electric communications; digital telephone sets. SUBSTANCE: device has switch stage 1, switch-stage power supply 2, three-winding transformer 3 whose first and second windings are cumulatively connected and third one is connected through its first lead to output of switch stage 1, to first lead of load resistor 8, to input of output signal shaper 9, to first lead of additional shunt resistor 10 and through second lead, to common bus and to second lead of load resistor 8. Power circuit of switch stage 1 is connected across output of power supply 2 whose input is connected to second output of first winding of transformer 3.. Input of switch stage 1 is connected to return-channel input bus; output of output signal shaper 9 is connected to output bus. Second lead of shunt resistor 10 is connected to first lead of switch 11 which passes current in one direction, its second lead being connected to common bus. Switch 11 may be made in the form of semiconductor diode whose anode is connected to second lead of shunt resistor 10 and cathode, to common bus. EFFECT: reduced amplitude of parasitic spikes into input line due to energy storage across transformer input windings during arrival of input pulses. 6 cl, 1 dwg