Telephone interface circuit

Details Telephone interface circuit Telephone interface circuit

2011-08-09

2011-08-09

Tsang, Fan (Department: 2614)

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

C379S386000, C379S393000, C379S394000

Reexamination Certificate

active

07995744

ABSTRACT:
A hook switch turns on a transistor by connecting the positive electrode terminal of a capacitor to a base terminal of a transistor in an off-hook state, causing a speech circuit and telephone lines to be connected. The hook switch turns off the transistor by disconnecting the positive electrode terminal of the capacitor from the base terminal of the transistor in an on-hook state, causing the speech circuit and the telephone lines to be disconnected. A holding circuit holds the voltage at the positive electrode terminal of the capacitor at a substantially fixed value by charging the capacitor with electric power supplied from the telephone lines in an off-hook state.

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patent: 2008/0037773 (2008-02-01), Fujiwara
patent: 2008/0285741 (2008-11-01), Fujiwara
Co-pending unpublished U.S. Appl. No. 12/268,895.

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