| 摘要 |
PURPOSE:To communicate with a master station network, by using an order line, when a remote line concentrator is not activated, through the use of a circuit tying the line concentrator and the master station network for a communication line and the order line switchingly. CONSTITUTION:Individual subscriber telephone sets a1-an are connected to a line concentrator RNW via subscriber circuits LC-1-LC-n. A telephone set a'1 connected with a teletypewriter TTY is provided for a special subscriber line 2, and this line 2 and the RNW are connected to a jack key lamp 1, and this key lamp 1 is provided with a switch which manually switches a PCM line connected to a digital trunk circuit DT as required, from the RNW to the line 2. The trunk circuit DT is connected to a master station network NW and when the RNW is not activated, the line 2 is connected to the network NW with the key lamp 1 to communicate the telephone set a'1 with a telephone set a'2 at master station. |
