Paul F Joyce

US Patent:

55331190, Jul 2, 1996

Filed:

May 31, 1994

Appl. No.:

8/250873

Inventors:

Gary E. Adair - Plantation FL
Paul Joyce - Boca Raton FL

Assignee:

Motorola, Inc. - Schaumburg IL

International Classification:

H04M 158

US Classification:

379391

Abstract:

A sidetone optimization circuit (230) provides the capability to adjust sidetone level received at a telephone handset to a desired level. A noise source (204) generates a noise signal that gets filtered by filter (206) in order to provide band limited noise to a telephone interface circuit (202). Telephone interface circuit (202) provides a sidetone signal (210), also known as a trans-hybrid loss signal. The trans-hybrid loss signal is filtered at filter (212) and transformed to a DC level at detector (214). The DC level is then compared to a predetermined threshold at comparator (224), and a variable impedance circuit (218) is adjusted until the DC level reaches the predetermined threshold in order to achieve a desired level of sidetone.