| 摘要 |
PURPOSE:To apply a device even when a line wire is not a rotary dial line, by attaching a change-over switch, a storage circuit, and a DTMF oscillation circuit, and utilizing a line device provided in a simplified exchange telephone system having extension call and central office holding functions. CONSTITUTION:A means 21 which switches a call signal system to a pulse dial system or a tone dial system alternatively, a DTMF oscillation means 23 which emits a tone dial, a connection means 2 which connects the oscillation means 23 to a central office line when a specific number is dialed from the extension telephone set in a case where the switching means 21 is switched to a tone dial side, a storage means 22 which stores an opposite number when the opposite number is dialed after switching the switching means 21 to the tone dial side and emitting the specific number from the extension telephone set, and a DTMF oscillation driving means 5 which drives the DTMF oscillation means 23 based on the opposite number and emits a tone dial signal to the central office line are provided. In such a way, the device can be connected to a DTMF line and also to the rotary dial line by applying simple improvement.
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