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:
Mar. 08, 1977
Filed:
Nov. 13, 1973
Robert M Thomas, Brockville, Ontario, CA;
Other;
Abstract
Communication system interface circuits for bidirectional transmission of signals between terminal sets, each interface circuit comprising a transformer including first winding means coupled through rectifier means and a low-pass filter to a first terminal set and including second winding means having end terminals coupled through diodes to the output of a high frequency inverter and having a center tap coupled through an inductance impedance to a neutral circuit point, a second terminal set being coupled across the inductive impedance. The first terminal set may be connected to a telephone subset with ringing and bias signals being applied in circuit with the inductive impedance. The indictive impedance includes transistor means controlled by an operational amplifier which is controlled from a resistance-capacitance phase-shift means, the impedance being equivalent to that of an inductance and a series resistance.