| 摘要 |
PURPOSE:To regulate the lower limit of a receivable frequency range adequately, only by modifying a conventional device slightly by generating a regulation voltage only when a band which should be regulated is selected. CONSTITUTION:A switching part 7 is composed of switching transistors TR71 and 72, and base ends are connected to switching terminals Bl and Bu for the VHF low band and UHF high band which need not be regulated. Consequently, the TR71 or 72 turns on in the reception of the VHR low band or UHF high band. Therefore, the TR turns on only during the reception of the VHF high band to extract a lower- limit regulation voltage Vhl. Further, this voltage Vhl is applied to the tuning- voltage application terminal 24 of a tuner 2 via a switching diode 8. Therefore, when the output voltage of a channel selection part 4 drops below the voltage Vhl, a diode 8 turns on and holds the tuning voltage at the voltage Vhl, thereby regulating the range of a lower-limit receivable frequency. |
