| 摘要 |
PURPOSE:To make it possible that any terminal device communicates with a center device urgently at any time independently of the communication state between other terminal devices and the center device, by transmitting an urgent communication request pulse from this terminal device when an emergency occurs in this terminal device to require the immediate transmission to the center device. CONSTITUTION:When the terminal device requires the urgent communication, the terminal device transmits the urgent communication request bit having a prescribed duration, which can be distinguished from other data bits distinctly, with a high level to a line during the period of the urgent communication request bit in the communication signal between other terminal devices 1, 2, and 3 and a center device CNT even if there is no idle time for communication and other devices 1, 2, and 3 and the center device CNT communicate with each other. When the high-level signal is received in the center device CNT, the center device CNT discriminates that the high-level urgent communication request bit signal is transmitted from some terminal device, and the device CNT sets the mode discrimination code of a supervisory and controlling signal to the urgent communication mode to transmit the signal to terminal devices 1, 2, and 3. Each terminal device which receives the supervisory and controlling signal of this urgent communication mode stops immediately the data transmission from its own station. |
