| 摘要 |
In tuning apparatus, a sensor senses when a tune indicating signal has been produced by the IF section so as to enable an adjusting circuit to change the tuning condition of the apparatus by a predetermined frequency step and then to disable the adjusting circuit if the tune indicating signal still is sensed following this frequency change so as to maintain the last-attained tuning condition. Alternatively, if the tune indicating signal no longer is sensed after the tuning condition has been changed by the predetermined frequency step, the tuning section is returned to its preceding tuning condition by this predetermined frequency step. Consequently, if the received signal is a high level signal at a frequency within a predetermined range from a broadcast frequency, the tune indicating signal is produced when the tuning condition of the tuning section differs from the broadcast frequency by this predetermined frequency step; and the tuning condition then is changed by this step so as to arrive at the desired broadcast frequency. If, however, the received signal is a low level signal, the tune indicating signal is produced only when the tuning condition of the tuning section coincides with a desired broadcast frequency, and then this tuning condition is changed by one step followed by a return of one step to the proper condition. |
