| 摘要 |
PURPOSE:To control the lower limit by means of a simple circuit, by connecting the parallel circuit of a resistance and a switch to the low potential side of a variable resistor for tuning, and opening the switch only when it is necessary to control the lower limit of the receivable frequency. CONSTITUTION:The channel selection part 4 is constituted of a band switching part 6 and a variable resistance 5 for channel selection. When the first switch S1 and the second switch S2 are switched, the prescribed voltage is applied to the tuner 1 from the resistance 5, and the selected band becomes receivable. When the switches S1, S2 have selected a VHF low band VL, the transistor 33 becomes off. Accordingly, in this case only, the resistance 31 is connected in series to the variable resistance 5, the lower limited voltage is set, and the lower limit of the receivable frequency is controlled. |
