| 摘要 |
PURPOSE:To firmly settle the state of the selector switch of a circuit even if switching instructions overlap by controlling the switching of the circuit according to the information of a switching operation deciding switch and the use state of a communication circuit. CONSTITUTION:A communication circuit use state monitoring means 15 monitors a cable 4 connecting the circuit selector switch 22 and a MODEM 3, and stores the use state information of the communication circuit 1 in a communication circuit state register 24. A selector switch operation deciding means 16 decides whether a switching operation is possible or not according to the information of a switching operation register 23 and the information of the communication circuit state register 24, and if possible, it operates a selector switch operating means 17. The selector switch operating means 17 operates a circuit selector switch 2 according to the instruction of the selector switch operation judging means 16. Thus, a switching operation can be stably performed.
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