George T Kufta

51033151, Apr 7, 1992

Mar 16, 1990

7/495234

George T. Kufta - Glenview IL
Carl W. Stacy - Elmwood Park IL

Zenith Electronics Corporation - Glenview IL

H04N 550
H04N 560

358198

A stereo television receiver includes a microprocessor for developing logic level control signals for controlling tuning, video processing and a LED stereo indicator. A sync separator circuit supplies a horizontal signal to a peak detector which supplies a logic level output signal to the microprocessor. An audio mute circuit includes a pair of transistor switches, one each coupled to the left and right audio channels. The switch base electrodes are coupled together and supplied through LEDs from two delay circuits. One delay circuit is activated by the LED stereo indicator logic level control signal and the other by a logic level output signal developed when a television signal is tuned. The period of the delay circuit activated by the tuning of a television signal is sufficiently long to permit a determination of whether a stereo or a monaural audio signal is present. The mute circuit eliminates annoying pops and clicks developed during monaural/stereo signal transitions and between the tuning of television signals.

46882529, Aug 18, 1987

Dec 19, 1985

6/811035

George Kufta - Glenview IL
David S. Tait - Addison IL

Zenith Electronics Corporation - Glenview IL

H04H 500

381 4

A TV SAP/stereo audio system includes a DC switch for selectively coupling the output of a stereo decoder and the output of a SAP detector to a stereo amplifier. A DC voltage, representative of the SAP carrier level, is developed and applied to a pair of threshold transistors. The lower threshold transistor is driven conductive when the DC voltage is below a first voltage and the upper threshold transistor is driven conductive when the DC voltage is above a second voltage. The threshold voltages are established by a pair of voltage dividers. A SAP control transistor is coupled to the collectors of the threshold transistors and is driven conductive when either threshold transistor is in conduction. The SAP control transistor is connected to the DC switch and prevents coupling of the SAP detector output to the stereo amplifier when it is conducting. A stereo cutoff transistor is coupled to the SAP control transistor for enabling the DC switch to couple the output of the stereo decoder to the stereo amplifier when a SAP mode is selected by a selector switch and the SAP control transistor is conducting.