| 摘要 |
PURPOSE:To reduce the quantity of generated noise to improve the service quality by adding an inform tone to a voice signal of the second subscriber with respect to amplitude to transmit this signal to the first subscriber until a channel is switched by the hooking operation of the first subscriber. CONSTITUTION:When a start signal S of incoming busy in is inputted from an input terminal 20, a timing generating circuit 21 generates a timing signal (t) of a prescribed period and outputs it to an inform tone generating circuit 2. The circuit 22 generates the inform tone of busy incoming having a prescribed frequency, which is started in zero phase, synchronously with the rise of the signal (t) and stops the report tone synchronously with the fall of the signal (t). Thus the intermitted inform tone is generated and is inputted to an adding circuit 23, and the circuit 23 adds the inform tone to the voice signal, which is inputted to an input terminal 12, from the second subscriber B to the first subscriber A with respect to amplitude and transmits this signal to the subscriber A. The voice signal from the subscriber A to the subscriber B is transmitted to the subscriber B as it is. Thus, the quantity of generated noise is reduced to improve the service quality.
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