Interface circuit to quickly establish a loop current

Details Interface circuit to quickly establish a loop current Interface circuit to quickly establish a loop current

1992-12-16

1994-07-12

Dwyer, James L.

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379377, 379399, H04M 322

Patent

active

053295846

ABSTRACT:
According to the invention, an interface circuit for quickly establishing a DC loop current in response to off-hook detection is provided by a circuit which uses a transistor, where its collector electrode is connected to the first one of the telephone lines; an emitter resistor connected between an emitter electrode of the transistor and the second one of the telephone lines; a bias resistor having a first terminal connected to the collector electrode; a Zener diode connected between a second terminal of the bias resistor and the second line; a first capacitor connected in parallel to the constant-voltage means; switching means connected between the second terminal of the bias resistor and a base electrode of the transistor for the switching means to be conductive in response to an off-hook signal; and charging means, typically formed of a series connection of a capacitor, a resistor and a Zener diode, connected in parallel to the bias resistor so as to allow a current to flow through the series connection to charge the first capacitor only during a transient of applying a Dc voltage from the telephone lines onto the transistor.

REFERENCES:
patent: 3748401 (1973-07-01), Pesz et al.
patent: 4015091 (1977-03-01), Rao et al.
patent: 4025729 (1977-05-01), Stone
patent: 4282407 (1981-08-01), Stiefel
patent: 4500754 (1985-02-01), Mackey
patent: 4535202 (1985-08-01), Meunier
patent: 4958371 (1990-09-01), Damoci et al.
patent: 5020100 (1991-05-01), Gardiner
patent: 5138658 (1992-08-01), Carter et al.
patent: 5140631 (1992-08-01), Stahl

Affiliated with

Also associated with

Rating

Interface circuit to quickly establish a loop current does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Interface circuit to quickly establish a loop current, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Interface circuit to quickly establish a loop current will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-402955