| 摘要 |
PURPOSE:To perform data communication through the use of an idle time of telephone, by providing a network controller with priority over calls, at the presence of off-hook of a telephone set, even during the operation of a data terminal device. CONSTITUTION:When a telephone set 200 is at off-hook, a current flows to a photo coupler 111 in an off-hook detector 110 through a resistor 173 for current limit. The photo detection side of the photo coupler 111 in which one end is grounded is conductive and a signal F changes to ''0''. An automatic dial section 140 detects off-hook through the signal change and off-hook is informed to a data terminal device 300 via a connection terminal 106. The device 300 stops the data communication through this result. On the other hand, when the signal F changes to ''0'', the output of an AND circuit 165 is changed to ''0'' and a relay 170 is restored. Thus, a loop current is cut off and the exchanger is restored after a prescribed time. The relay 167 restores through a delay circuit 150 after the end of restoration of the exchanger. |
