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:
Dec. 06, 1983
Filed:
May. 20, 1982
Applicant:
Inventors:
Edward C Kelm, Pasadena, CA (US);
Stephen Kurtin, Sherman Oaks, CA (US);
Assignee:
Other;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
H04M / ;
U.S. Cl.
CPC ...
179 / ; 179 / ; 179 / ;
Abstract
A hold circuit for use with Dual Tone Multi Frequency telephone systems including a bistable circuit connected across the telephone line, the ON state drawing sufficient current from the telephone line to hold the circuit and the OFF state being substantially infinite impedance, a tone detection circuit which triggers the bistable circuit ON when the two frequencies produced by the '*' button are sensed, and a means for triggering the bistable circuit OFF responsive to the drop in line voltage due to a telephone on the line being taken off-hook.