| 摘要 |
PURPOSE:To realize a countermeasure to emergency call regardless of the occurrence of a fault, by setting an emergency circuit which is terminated to a plug at an attendant board and at the same time connecting each terminating circuit to the incoming trunk of an exchanging device via a jack. CONSTITUTION:The contact groups AK1, RK1 and LK1 whose working states are detected by a scanner SCN as well as the contact groups AK2, RKa and LK2 which are connected to an emergency circuit EMT are added to an answer key AK, a rering key RK and a release key LK which are installed to an attendant board ATT. An end of the channel of the circuit EMT is connected to a talking circuit of the ATT; and the other end is connected to a chip P1 and a ring P2 of a plug P respectively. In such constitution, if the exchanging device has a fault, a circuit L is isolated from an incoming trunk ICT and switched to the circuit EMT just by inserting the plug P into a jack J. |
