| 摘要 |
PURPOSE:To make a circuit configuration simple and small-sized by detecting a direction of the two-wire trunk line by means of a photocoupler which has been inserted into the diode bridge, in the outgoing connection trunk for negating a DC magnetic flux. CONSTITUTION:The diode bridges D2-D5 are provided between the primary windings L0, L1 of the hybrid transformer HYB1 connecting the two-wire trunk line side and the switchboard side service line, and the trunk line side, so that one rectifying current only flows into said primary windings, a magnetic flux by the primary winding current is negated by making a current flow into the tertiary winding L3 under the control by the Hall element Ho means, and also it is detected by the photocoupler PCo means which has been inserted and connected in the diode bridges D2-D5. Accordingly, the tertiary winding L3 is enough by one, and also a relay with high sensitivity for supervising the block and release becomes unnecessary. |
