| 摘要 |
PURPOSE:To apply the data communicating function to the telephone set under the dial pulse signal system with a simple constitution by generating the PB signal which can be controlled by the push-button switch at the time of connecting the line by the detection of the line connecting condition between callers. CONSTITUTION:A line condition detecting circuit 3, when the non-polar calling electric current is detected, changes over and connects a keyboard 2 from a DP signal generating circuit 4 to a PB signal generaiting circuit 5. As the result, the PB signal can be controlled by the keyboard 2, and by applying the PB signal to the transmitter, the data communication can be realized besides the usual calling. Next, when accompanying the completion of the communication, the release is obtained, the line condition detecting circuit 3 changes over and connects the keyboard 2 from the PB signal generating circuit 5 to the DP signal generating circuit 4.
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