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:
Sep. 28, 1993
Filed:
Oct. 25, 1991
Arthur B Williams, Smithtown, NY (US);
Coherent Communications Systems Corp., Hauppauge, NY (US);
Abstract
A digitally programmable attenuator balances impedance across a two to four-wire hybrid to reduce echo. The hybrid can interface a two-wire bi-directional telephone line, used for both transmit and receive signals with four-wire circuits having separate unidirectional transmit and receive signal paths. The four-wire circuit interfaces the two-wire circuit through a transformer. Optimum isolation is obtained by setting impedance Z.sub.BAL equal to the impedance of the line including the transformer (Z.sub.LINE). The invention eliminates manual or customized individual adjustment of Z.sub.BAL by a set up technician by use of a digitally controlled attenuator to electronically vary the value of Z.sub.BAL in a highly precise fashion. The programmable attenuator provides an input voltage to a buffer voltage-follower amplifier. The output of the follower amplifier is coupled to a known impedance to limit current flow through the impedance and consequently, current flow through Z.sub.BAL. Data to the attenuator is provided from a DSP programmed to sense and automatically converge to a balanced condition.