The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 31, 1988
Filed:
Nov. 14, 1986
Applicant:
Inventor:
Peter F Blomley, Bishop's Stortford, GB;
Assignee:
STC Plc, London, GB;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
H04M / ;
U.S. Cl.
CPC ...
379395 ; 379387 ;
Abstract
To provide an adequate dc supply to the electronics of a telephone, when on hook or off hook, there is a transistor (T2) with its emitter-collector path in one line wire, and a storage capacitor (Cpsu) across the input to the telephones's circuits. This capacitor is charged up and maintains dc supply when the line voltage (at A) falls below a preset level. The base of this transistor is connected via another transistor (T1) to the other line wire. The speech output (V.sub.IN) is connected via an operational amplifier (A) to the base of the second transistor (T2). Hence the dc supply and the speech output are in parallel.