| 摘要 |
<p>PURPOSE:To store an existing terminal exclusive for incoming call into a time division switchboard without reconstruction, by controlling a current supplying circuit with the output of an AND of the negtive conditions of a control line for reduction of power consumption and the affirmative conditions of a control line for the current supplying circuit. CONSTITUTION:A control program of a central processing controller 11 drives both a power consumption reduction control line 6 and a current supplying circuit control line 7 when a terminal T is free. Thus a general subscriber terminal SUB has an originating call, and this call is detected by a loop monitor circuit 5 if a short circuit is secured for the DC resistance between lines A and B. For a subscriber circuit 12 of the terminal exclusive for incoming call, a current supplying circuit 4 is controlled with the output of an AND circuit 13 of the negative conditions of the line 6 and the affirmative conditions of the line 7. Thus the circuit 4 of the circuit 12 is turned off although the control program drives the lines 6 and 7 when the terminal is free and regardless of a general terminal or the terminal 12 exclusive for incoming call. As a result, no current is supplied even with a connection of the terminal T short-circuited between the lines A and B in the normal mode. Thus it is avoided that a loop is detected by the circuit and then regarded as an originating call.</p> |
