| 摘要 |
PURPOSE:To eliminate the need to provide a sound source for an audible ringing tone separately by frequency-dividing a specific frequency signal for calling and thus generating the audible ringing tone of a low frequency signal. CONSTITUTION:A communication circuit is provided with an auxiliary order circuit separately from a main circuit. A service channel signal 2 is sent to the order circuit. A band-pass filter 11 filters out a specific frequency signal for order circuit calling in the service channel signal 2. When the output signal of the band-pass filter 11 is higher than a prescribed level, a comparator 12 generates a rectangular wave. This rectangular wave is frequency, divided to obtain a signal of adequate audio frequency. This signal is used as an audible ringing tone to allow a speaker 15 to sound. |
