| 摘要 |
PURPOSE:To prevent multiple access to an access bus that a subscriber telephone set circuit and a subscriber line circuit access by installing a control bus in prallel to the access bus, and providing a control circuit which detects whether the access bus is in use or not. CONSTITUTION:The control bus C is installed in parallel to access buses A and B, and access to the access buses A and B is all attained through the control bus C. Namely, the control bus C is held at a level H when neither access bus A nor B is in use and at a level L when the access buses A and B are in use. A control circuit CONT decides on whether the access buses A and B are used or not from the output of a buffer BUF1, and when they are not used, a relay RL is energized under the command of the controller CC of an electronic exchange to connect its subscriber line SLC to the access buses A and B and the control bus is held at the level L to inhibit other subscriber lines from being connected. |
