| 摘要 |
PURPOSE:To confirm the connection of a circuit and to securely instruct that a communication is ready by transmitting and receiving a fixed pattern signal between connected data terminal interface devices, and switching transmission lines in the data terminal interface devices. CONSTITUTION:When data terminal interfaces 1b and 1c detect the 1st fixed pattern signal for confirmation through a connected circuit by monitoring circuits 14, their pattern signal generating circuits 12 generate and send out the 2nd fixed patterns to the circuit side. The data terminal interface devices 1b and 1c at the time of detecting the 2nd fixed pattern signals by the monitoring circuits 14 perform switching by origination-side switching circuits 13 and termination-side switching circuits 16 so that the fixed pattern signals from the sending data terminal interface devices 1b or 1c is sent out to the opposite data terminal interface device 1c or 1b. Consequently, the instruction of the communication ready state is sent to a data terminal device 2 at the same time.
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