| 摘要 |
<p>A communication by an auxiliary terminal (AUX) is performed using a voice signal line taken out by a switch (SW) having eight circuits and six contacts or having eight circuits and three contacts. Then, an automatic changing over circuit (SS) which is isolated from the voice signal line in relation to DC and is coupled to it in relation to AC detects the completion of the communication and the restoring connection is performed. By this configuration, communication can be performed by connecting the auxiliary terminal with an exchange called an energy-saving type and outputting only AC signals, and the restoring connection can be performed automatically after the completion of the communication. That is, the device for changing over and restoring automatically a telephone circuit whose application is not limited can be provided.</p> |
