Telephone line loop current regulator

Details Telephone line loop current regulator Telephone line loop current regulator

1989-07-07

1991-05-28

Ng, Jin F.

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379377, 379380, H04M 100

Patent

active

050201000

ABSTRACT:
A telephone line loop current regulator combines the functions of current regulation, current detection, loop disconnect signalling and speech switching. It comprises a gyrator circuit formed by resistor (R1), capacitor (C1), transistor (T1) and resistor (R3). Loop current is regulated by transistor (T1) and resistor (R3) while loop current detection is achieved by monitoring the voltage across resistor (R3) by an opto-diode which forms part of an opto-electronic coupler (OP2). Speech switching is performed by transistor (T3) which also monitors the voltage across resistor (R3) so that speech is switched onto the line via transformer (TR1) when d.c. loop current is present. Line seizure and loop disconnect signalling are carried out by switching the opto-coupler (OP1) to turn the transistor (T1) on and off.

REFERENCES:
patent: 4190745 (1980-02-01), Jusinskas, Jr. et al.
patent: 4230912 (1980-10-01), Lee et al.
patent: 4535202 (1985-08-01), Meunier

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