Battery boosted dial memory

Details Battery boosted dial memory Battery boosted dial memory

1990-02-01

1992-05-12

Dwyer, James L.

Telephonic communications

Subscriber line or transmission line interface

Network interface device

379387, 379355, H04M 1900

Patent

active

051134349

ABSTRACT:
A telephone subset has a dial circuit (2) which can be powered from the exchange line (11, 12) via a regulated voltage terminal (VDD) of an associated transmission circuit (3) when the subset is OFF-HOOK and the line voltage is above a threshold voltage. When the subset is ON-HOOK, the dial circuit (2) is powered from a battery (B1) via a first switching circuit (TR2, TR3, R3). A hook-switch (HS) hold the first switching circuit OFF when the subset is OFF-HOOK to isolate the battery (B1) from line voltage. If the line voltage falls below the threshold when OFF-HOOK, a current sensing resistor (R4) switches a second switching circuit to connect the battery (B1) to the dial circuit (2) while the regulated voltage terminal presents a high impendance to isolate the battery from line voltage.

REFERENCES:
patent: 4272650 (1981-06-01), Bolgiano et al.
patent: 4532382 (1985-07-01), Pommer, II
patent: 4647787 (1987-03-01), Pommer, II
patent: 4653088 (1987-03-01), Budd et al.
patent: 4813072 (1989-03-01), Moses et al.
patent: 4847899 (1989-07-01), Hikida
patent: 4961220 (1990-10-01), Tentler et al.

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