| 摘要 |
PURPOSE:To prevent a line from being occupied owing to trouble, etc., by providing a monitoring function for a request-to-send signal (RS) and a carrier to plural terminal devices connected on a multidrop basis. CONSTITUTION:The modem 2 of a terminal device is provided newly with a carrier transmission inhibiting means 4, a carrier detecting circuit 5, and a time detecting circuit 6. The means 6 is started with the RS (request to send) and when no SD (send data) is detected within a specific time, the means 4 is operated to stop the transmission of the carrier. The means 6 is started after the transmission of SD and when the RS is still sent even after a specific time is elapsed, the means 4 stops the transmission of the carrier. The means 6 is started even when the means 5 detects the carrier and even when the stop of the carrier is not detected even after the specific time, the transmission of the carrier is stopped by the means 4. Further, even when a switch 8 is placed on its right side to set a test state continuously, the means 4 and 6 operate to stop the transmission of the carrier.
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