| 摘要 |
PURPOSE:To obtain a channel switching system which does not require a special mounting space, by controlling so as to execute the opening and closing operation in reverse to the switch contact concerned of the trunk switch, in the event of switching the trunk of the automatic switchboard. CONSTITUTION:In case an office side subscriber is talking with an extension subscriber, if it is required to send out a holding tone to the office side subscriber, the central control unit CC detects the holding tone condition, discriminates it, operates the driving transistors Q0, Q1, and moreover, the unit CC controls its driving current direction switching circuit TR, and makes a pulse current I in the reverse direction to the channel set time flow to the switch magnet TM and the cut-off magnet CM. Accordingly, the cut-off contacts COA, COB are closed, and the channel of the trunk TRK is changed to the holding tone source HDT side. In this state, when the call start condition has been arranged once again, the central control unit CC discriminates it, makes a pulse current I in the reverse direction to the channel switching time flow to each magnet TM, CM, and restarts the call between the office side and extension subscribers. |
