| 摘要 |
PURPOSE:To simplify the circuit constitution, to reduce the number of circuit parts and an occupied area by using the reference frequency oscillator circuit of a partial oscillator circuit as the reference frequency of the voltage controlled oscillator circuit of a call signal detecting circuit composed of a PLL circuit. CONSTITUTION:When a call signal is included in the output of a demodulator circuit terms of the call signal detecting circuit 5, said signal is phase-compared with the output of the voltage controlled oscillator circuit 28 by a phase comparator 26. The circuit 28 oscillates with the output signal of the reference frequency oscillating circuit 24 of the partial oscillating circuit 25, or a signal available from voltage-dividing said output as a reference frequency. Here, when the call signal is equal to the output of the circuit 28, the PLL circuit locks the signal in the almost same manner as the partial oscillating circuit 25. The detection sensitivity of the call signal of the PLL circuit causes an amplifier circuit 29 to change an amplitude degree and to transmit the output to a comparator 30. When the output of the circuit 29 is less than a reference voltage, the circuit 29 generates the output at a high level. Thus a call sound generating circuit 6 is driven, and a call sound is generated from a speaker 4. |
