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. 09, 1997
Filed:
Dec. 05, 1995
Randy D Pfeifer, Warrenville, IL (US);
NCR Corporation, Dayton, OH (US);
Abstract
A software-implemented bridging routine is provided for a full duplex audio telephone system comprising units A, B and C. of which only unit A need have at least two lines and be full duplex. Unit A receives and speaker-reproduces an audio signal B+C that echoes with a time delay dt.sub.1 and is detected by unit A's microphone as a signal k.sub.b Bdt.sub.1 +k.sub.c Cdt.sub.1, where k.sub.b and k.sub.c are co-efficients. Unit A's host software determines time dt.sub.1 and generates a delay dt.sub.2 .apprxeq.dt.sub.1. Unit A's host processor sums its own microphone output with a signal generated by a non-destination unit that is delayed by time dt.sub.2. Thus, when communicating with unit B, unit A's software generates a host processor output signal A+k.sub.b Bdt.sub.1 +k.sub.c Cdt.sub.1 +Cdt.sub.2. The k.sub.b Bdt.sub.1 echo component is removed by unit A's AEC, which is coupled between units A and B. This causes unit B to receive the signal A+Cdt.sub.2 +k.sub.c Cdt.sub.1 from unit A. Since dt.sub.2 .apprxeq.dt.sub.1, user B hears voice A summed with a slightly delayed voice C (e.g., Cdt.sub.2) superimposed with an attenuated in-phase version of voice C (e.g., k.sub.c Cdt.sub.1). User B thus hears user A's voice and user C's voice conversing naturally in a full duplex manner. Similarly, B hears user A and user C conversing, and user C hears user A and user B conversing. In this fashion, full-duplex operation is achieved without using hardware bridge circuitry.