| 摘要 |
PURPOSE:To decrease the probability of busy state and to inform an emergency signal surely, by switching the operating line into the 2nd line for plural telephone lines for automatic redialing when a monitor station discriminates the line to be busy, and performing redialing after switching the telephone lines sequentially. CONSTITUTION:When telephone lines L11, L21 are busy, the busy state is detcted at a busy state detection circuit 3 and an automatic redialing control circuit 5 is driven with an output signal bs. The circuit 5 drives an automatic dial circuit 1, changes over a switch C in the position shown in dotted lines, connects other telephone lines L12, L22 and starts the calling of the monitor station. Thus, when a response signal is returned from the monitor station, an emergency signal is transmitted, and if the monitor station is busy, the lines L12, L22 are switched again and redialed on the lines L11, L12. |
