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:
Jan. 15, 1991
Filed:
Sep. 15, 1989
Patrick J McGarry, West Chester, PA (US);
Mars Incorporated, McLean, VA (US);
Abstract
A method and apparatus to enable a low power telephone controller to operate with either a carbon microphone or a dynamid microphone is described. A jumper in a preamplifier and filter circuit is preset to accommodate the audio transfer characteristics of one or the other type of microphones. For either microphone, a small DC current of less than 500 .mu.A is used to sense the presence of either type microphone and serves the dual role of biasing the carbon microphone to the appropriate level to be amplified so that the input to an audio circuit in the controller us very nearly the same for either microphone. The audio circuit then processes and dynamically balances the signal to the telephone line, where it is output.