| 摘要 |
PURPOSE:To reduce effectively a channel selecting time without skip channel selection by detecting whether a broadcast station exists in a frequency step and changing over the frequency step into a narrow band to attain channel selection and tuning when the broadcast station exists. CONSTITUTION:When a broadcast station is detected in the frequency step, an output ST1 of a detector 25 goes to a high (H) level and an output ST2 of a detector 24 goes to a low ''L'' level or ''H'' level. When the output ST1 of the detector 25 goes to ''H'' level, the frequency dividing period of a programmable frequency divider 14 is controlled so that the channel selection frequency step is changed into the narrow band, e.g., 25kHz by a controller 12. When the broadcast station is detected in the frequency step of the narrow band and the output ST2 of the detector 24 goes to ''H'' level, the controller 12 judges that the tuning is finished and the change in the frequency dividing period of the programmable frequency divider 14 is stopped. Then the output of the detector 24 is demodulated and a sound signal is obtained. |
