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. 02, 1978
Filed:
May. 25, 1977
Milton Luther Embree, Reading, PA (US);
John Francis O'Neill, Boulder, CO (US);
Bell Telephone Laboratories, Incorporated, Murray Hill, NJ (US);
Abstract
A local battery feed circuit for telephone station sets comprises two half circuit portions substantially symmetric about an imaginary line midway between the TIP and RING telephone lines. Each half circuit includes a current drive amplifier including a pair of up-down emitter follower transistors and a driver transistor. A coupling capacitor and matched resistors provide common mode interference reduction without degrading differential mode signals. Power supply noise is substantially eliminated by transistors in each half circuit arranged to produce an a.c. current equal and opposite to that generated from the power source.