| 摘要 |
PURPOSE:To realize a control for the receivable frequency range at a channel selection part only, by connecting resistors in series and parallel to a variable resistor for channel presetting in linkage with a band switching action and then limiting the upper and lower limits of the tuning voltage variable range. CONSTITUTION:For a preset part 6, a semifixed resistors 63 and 65 can be connected in parallel and series to a conventional variable resistor 62 in linkage with a band switching action. As a result, a parallel connection is secured for the resistances having the set values although the resistor 62 is turned up to its full upper limit in case the band with which the upper limit frequency must be regulated is received. Furthermore the pulse duration of an output pulse signal is reduced down to a level lower than a certain value. In case the band with which the lower limit frequency must be regulated is received, the resistor 63 is connected in series to the registor 62. Thus resistance value, i.e., the pulse duration of the output pulse signal is never set at zero, and accordingly the upper and lower limits are regulated for the tuning voltage which is applied to a tuner. |
