| 摘要 |
PURPOSE:To obtain a selective calling device which can show the presence or asbence as well as transmit the message to some extent by detecting the message signal frequency following the tone sequence for selective calling through the scanner and then displaying the signal frequency. CONSTITUTION:The high-frequency signals which are modulated with the fixed tone signal are received at receiver 22 and then led to filter 23 which synchronizes with the first frequency of the sequence corresponding to the self-calling signal. The tuning frequency of filter 23 is altered sequentially according to the subsequent self-calling tone sequence through detector 24, decoder 25 and frequency control circuit 33. When decoder 25 detects the self-calling tone sequence, alarm circuit 27 is started for display. At the same time, scanner 34 is started to secure synchronization with the message tone signal for filter 23. The number and others of this tone signal is displayed at display unit 26 through decoder 25. |
