Line circuit for network junctor

Claim 1

A line circuit for network junctor, comprising loop current interrupting means allowing dialling including regulating means for maintaining said loop current about a predetermined threshold and for presenting a high impedance for the telephone frequencies and a low impedance for the ringing currents, said regulating means comprising two transistors forming a Darlington assembly, the first transistor receiving on its base a loop opening or closure control pulse and being in series with a first resistor, the base of the second transistor and the collector of the first transistor being connected by a second resistor, and means for stabilizing the base voltage of said second transistor in order to raise the impedance of said regulating means in the telephone band, means for controlling said regulating means disposed in parallel on said first resistor and comprising a third transistor whose base is connected to the emitter of said first transistor and whose collector is connected to the base of said second transistor, the emitter of said third transistor being connected to said first resistor via a diode in order to improve the regulation for the low voltages.