| 摘要 |
PURPOSE:To reduce the cost of a channel selector, by installing a synthesizer to a channel selecting circuit that receives two different frequencies. CONSTITUTION:A set of a programmable frequency divider 9 and a frequency comparator 11 within a channel selecting circuit to a double system receiving circuit of a master TV and a slave TV or a video tape recorder, etc. When the channel of the master TV is selected, switches 14 and 15 are set at the side (a). In this case, a synthesizer circuit is formed by a voltage control oscillator VCO2a, the divider 9 and the comparator 11 to carry out the channel selection. Then the switches 14 and 15 are set at the side (b) for the channel selection of the slave TV, and thus the output of a voltage generator 13a is fixed at the master TV side to the oscillator VCO2a. Thus a switch 17 is closed to actuate an AFC circuit 19a, and the receiving state is maintained. |
