H - Electricity – 04 – B
Patent
H - Electricity
04
B
365/7
H04B 1/16 (2006.01) H03J 3/18 (2006.01) H03J 5/02 (2006.01) H03J 7/06 (2006.01) H04N 5/44 (2006.01)
Patent
CA 1057432
CHANNEL SELECTING APPARATUS ABSTRACT OF THE DISCLOSURE In a channel selecting apparatus for a television receiver having an electronic tuning tuner for changing the receiving frequency in accordance with an analog control signal applied thereto; a memory has a plurality of addresses for storing respective digital codes each identifying a respective channel and which are selectively activated so as to effect read out of the respective channel identifying digital code to a digital-to-analog converter which converts the same into a respective analog control signal for the tuner, deviation of the receiving frequency, as established in response to the analog control signal, from the correct receiving frequency for the channel identified by the digital code then being read out of the memory is detected, and, in response to a detected deviation within a pull-in range of an automatic fine tuning (AFT) circuit, the latter changes the digital code applied to the converter in the sense for removing such deviation and thereby achieving the correct tuned condition. Further, when the detected deviation is outside the pull-in range of the AFT circuit, sweeping changes are made in the digital code applied to the converter for cyclically varying the receiving frequency and thereby bringing the latter at least into the pull-in range of the AFT circuit. Preferably, the sweeping changes in the digital code are effected first by relatively small amounts and, if the receiving frequency is not thereby brought into the pull-in range, then by relatively large amounts. When the detected deviation exceeds a predetermined amount, whether within or outside of the pull-in range, the modified digital code resulting from the operation of the AFT circuit and/or from the sweeping changes in such code is stored in the memory in place of the read out digital code resulting in such deviation. - 1A -
266079
Mogi Takao
Okada Hisao
LandOfFree
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