| 摘要 |
PURPOSE:To discriminate which telephone set rings by changing individually a call signal to a sound calling telephone set. CONSTITUTION:The circuit consists of an oscillating circuit 1 of a call tone, an analog switch intermitting an output signal of the oscillating circuit 1, a keying pulse generating circuit 2 generating a keying pulse controlling the analog switch and a frequency selecting circuit 3 designating the frequency of the keying pulse. A call signal transmitted from the oscillating circuit 1 is outputted to the sound calling telephone set 6 via the analog switch 4. Since the analog switch 4 is turned on/off by an output of the keying pulse generating circuit 2 generating a pulse having a frequency designated by the frequency selecting circuit 3, an output 5 becomes a signal intermitted in response to the period of the keying pulse. The frequency selecting circuit 3 of each calling signal generating circuit for sound calling telephone sets installed on the same floor is set so as to generate different ring tones depending on each sound calling telephone set. |
