| 摘要 |
PURPOSE:To shorten the time to be elapsed before rush current lowers below a predetermined level, by interrupting control signal to be fed from a photoelectric conversion circuit when power supply is started with reverse polarity thereby increasing impedance of a rush current suppressing means. CONSTITUTION:A rush current suppressing means 4 having variable impedance is connected between lines L1, L2 connected to a power supply means 5. A conversion circuit 3 for subjecting a control signal to electricity-light conversion and thereafter to light-electricity conversion is connected to the suppressing means 4, and the impedance of the suppressing means 4 is set lower than a predetermined level when the control signal is being fed. When power supply direction is changed through a power supply means 5 so as to start power supply with reverse polarity, the control signal is interrupted and the impedance of the suppressing means 4 is increased. With such arrangement, time necessary for establishing a subscriber line link can be shortened in case of a subscriber line transmission system. |
