| 摘要 |
PURPOSE:To reduce a loss of a trunk circuit, by detecting a secondary winding current direction of a repeating coil, making a primary winding current flow in the opposite direction of the secondary winding current, controlling the direction to erase a magnetic flux generated by the secondary winding current, and making a diode, etc. unnecessary. CONSTITUTION:To secondary windings 3, 4 of a repeating coil 1 of the line side, a trunk circuit of an automatic telephone exchange is connected, and to one end of these windings 3, 4 photocoupler light emission diodes 21, 22 of a photocoupler are connected, and a current direction of the windings 3, 4 is detected by the diodes 21, 22. Photodetecting transistors 25, 26 for photodetecting the light of these diodes 21, 22 are placed on a primary winding current inversion driving circuit 30, and to the base of these transistors 25, 26, relays 28, 29 are connected. Relay contacts 28', 28'' and 29', 29'' of these relays 28, 29 are connected to a primary winding 2 of the repeating coil 1. Subsequently, a current of the winding 2 is made to flow in the opposite direction of a current of the windings 3, 4, a magnetic flux generated in the windings 3, 4 is erased, and a service loss of the trunk circuit is reduced. |
