| 摘要 |
PURPOSE:To use the main wire number display function part, which is used conventionally, commonly to display an extension number by providing a circuit which interfaces the extension subscriber's number to the B board when the extension subscriber is connected to the B board in the telephone exchange. CONSTITUTION:When incoming to B board 8 through main wire trunk 5 exists and the operator operates a number displaying key for obtaining the main wire number, earth is sent to number expansion circuit 9 through the route of position circuit 7, board trunk 6 and control line (a), and the main wire number is sent to interface 10 and position register 11 and is displayed on B board 8. When the operator dials an extension number, it is stored in register 11 and is connected through route (2) by common control unit 4, and the extension subscriber's number operates the key again and wakes up number expansion circuit 9 through route (b) to display the extension number similarly to the main wire number, and the extension connected actually is displayed even if it is representative number. |
