Abstract: A peak-valley detector of an analog signal which provides a digital output of the analog signal. A digital counter is used having an output coupled to a digital-to-analog convertor. The output of the digital-to-analog convertor is compared to an input analog signal. The output of the comparator is used to control the input of a clock signal to the counter. A selective invertor controls whether the comparator's output allows counting for signals above or below the digital-to-analog convertor's output level.

Abstract: A television receiver has provisions for a second audio program (SAP) and an indication for signifying when the SAP is present and a muting circuit for muting the SAP, both in response to the output signal of a SAP detector. A filter capacitor is coupled to the detector output to prevent flicker of the indicator due to noise. To prevent the filter capacitor from incorrectly maintaining an indication of the presence of a SAP, thereby preventing proper SAP muting, when a new channel is selected, channel change signal causes a semiconductor switch to discharge the filter capacitor. A SAP defeat switch coupled to the SAP provided the SAP detector output is to defeat the SAP when stereo is being received. To prevent the filter capacitor from discharging to rapidly and thereby creating an audible transient when either the defeat switch or channel change switch is operated, a resistor is coupled between the SAP detector output and the common junction of the SAP defeat and channel change switches.