Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1985-02-25
1986-12-09
Ng, Jin F.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
455212, 455221, H04B 110, H04B 116
Patent
active
046285393
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.
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Ahmed Adel A.
Emanuel Peter M.
Ng Jin F.
RCA Corporation
Whitacre Eugene M.
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