| 摘要 |
PURPOSE:To enhance the frequency precision at a preset time and prevent broadcast signals of freuencies close to each other from being led into adjacent channels in the channel selection mode, by changing a comparison voltage width in accordance with the automatic preset mode or the channel selection mode. CONSTITUTION:In the preset mode, output signals S2 and S3 of a window comparator 40 are inputted to an AFT control part 51, and channel selection information for these signals in a specific state is inputted to a memory part 52. A mode switching signal S4 and a channel selection signal S5 are inputted to the memory part 52 also. In the channel selection mode, these input information are processed by a prescribed program and are converted to an analogue signal by a D/A converting part 53, and a tuning voltage signal S6 is obtained and outputted. The tuning signal S6 is inputted to a filter circuit 60, and the circuit 60 outputs a tuning voltage S7 which determines a channel selection frequency, and this tuning voltage S7 is applied to a variable capacitance diode of a tuner 10 to determine a receiving frequency. |
