| 摘要 |
PURPOSE:To reduce the current consumption of a circuit by storing a waveform of a dial tone in advance while being converted into a digital data and outputting the waveform of the dial tone based on the digital data when the dial tone is generated. CONSTITUTION:A ROM 20 is a dial waveform data storage ROM, in which 10 kinds of dial tones corresponding to dial numbers 0-9 of a telephone set are stored as digital data and outputs a dial tone (digital data) corresponding to the telephone number based on the address designation of a ROM control circuit 19. Then a demodulation circuit 13 and an OPF 14 restore the digital signal into a smooth analog signal, that is, the original waveform of the dial tone, the result is amplified by an amplifier 15 and outputted in voice from a speaker 16. Since the waveform of dial tone is stored in the ROM 20 while being converted into the digital data in this way, it is not required to bring the frequency of the oscillator 1 into a high frequency (nearly 3.5MHz) and lots of frequency division stages are not required.
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