| 摘要 |
PURPOSE:To avoid system-down even if a DR signal is made active independently and to attain initialization of line properly even with misconnection to a line by providing a line supervising means whose operation is started when only one of MODEM preparation end signals outputted from two network control circuit control sections is active and inhibiting a terminal preparation end signal when the said MODEM preparation end signals are both not in the identical state after a prescribed time is elapsed. CONSTITUTION:When an NCU 12 is called and the NCU 12 makes a CI signal 18 active, an NCU control section 16 confirms that an ER signal 46 is made active, makes both a DR signal 21 and a CML signal 23 active and a public communication line 9 is switched from a subscriber's telephone set (not shown) of the NCU 12 to an MODEM 40. When the NCU 12 is started in error, since the DR signal 22 is not made active, a timer 43 makes its output 44 inactive, the ER signal 20 is inhibited by an AND gate 45, an ER signal 46 is made inactive and the NCU control section 16 outputs the DR signal 21 and the CML signal 23 as inactive signals. The NCU 12 receiving the inactive CML signal 23 switches the public communication line 9 from the MODEM 40 to the subscriber's telephone set (not shown) of the NCU 12 to attain initialization. |
