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. 19, 1981
Filed:
Sep. 04, 1979
Raymond G Taylor, Shreveport, LA (US);
Western Electric Company, New York, NY (US);
Abstract
The loop current (I.sub.X) of a telephone set speech network (1) is automatically initialized at a desired level independent of the central office voltage applied to the input terminals (12, 13) of the set and thus independent of transmission line loop length and other variables. For this purpose, a variable conductance device (20), sush as a Darlington driver (Q1), is connected between the input terminals and the speech network so as to establish a loop current at a circuit node (N1) that is a function of the supply voltage and the conductivity of the device. The loop current is monitored, as by a Schmitt trigger circuit (30), and the conductance of the device (20) is varied accordingly so as to initialize the loop current at the desired level, as by selectively connecting a plurality of resistors (R2 . . . R7) individually and collectively between a base node (26) of the driver (Q1) and the ring lead (17) of the set.