Telephone in-use indicator

Details Telephone in-use indicator Telephone in-use indicator

1993-02-23

1995-06-06

Dwyer, James L.

Telephonic communications

Substation or terminal circuitry

Visual signalling

377162, 377163, 377164, H04M 172

Patent

active

054229472

ABSTRACT:
A telephone in-use indicator having a diode bridge which is connected to a telephone line. The diode bridge ensures than an input signal from the telephone line is at a constant polarity. An inverter is connected to the diode bridge and receives a signal from the telephone line through the diode bridge. The inverter operates to invert the signal received from the telephone line. An oscillator receives a signal output from the inverter. A light emitting diode is connected to an output of the oscillator and is intermittently driven by the oscillator. A power source powers the inverter, oscillator and light emitting diode. When one telephone extension along the telephone line is changed from an "on-hook" to an "off-hook" condition, a drop in voltage is detected. As a result, the light emitting diode is intermittently driven by the oscillator to thereby provide an indication that a telephone line is in use.

REFERENCES:
patent: 3951248 (1976-04-01), Feiner et al.
patent: 4169217 (1979-09-01), Szanto et al.
patent: 4546214 (1985-10-01), Laing
patent: 4647723 (1987-03-01), Voorhies
patent: 4723279 (1988-02-01), Field
patent: 4726048 (1988-02-01), Waldman et al.
patent: 4777645 (1988-10-01), Faith et al.
patent: 4802207 (1989-01-01), Uchida
Engineer's Notebook II, Integrated Circuit Applications, Forret M. Mims III, 1982 Archer.

Affiliated with

Also associated with

Rating

Telephone in-use indicator does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Telephone in-use indicator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Telephone in-use indicator will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-993277