| 摘要 |
PROBLEM TO BE SOLVED: To enable stable communication from a slave unit to a master unit by keeping a line current flowing in a transmission line from increasing as the load current of the slave unit fluctuates stepwise. SOLUTION: A monitoring system has a plurality of slave units connected to transmission lines 12a, 12b drawn out of the master unit and serving also as current supply lines, and performs monitoring by transmitting UP signals from the slave units to the master unit in a current mode. A current fluctuation control device 20 is provided on the slave unit side that is regarded as a load device 25. The current fluctuation control device 20 includes a constant current circuit 52 which increases a line current I1 linearly as the load end voltage E1 of a fluctuating load 50 drops, and a capacitor C1 connected in parallel with the fluctuating load 50 and controlling the stepwise changes of the line current by means of the constant current circuit 52 by slowly changing the load end voltage E1 according to a discharge time constant or a charge time constant through a charge or a discharge upon the stepwise changes of a load resistance. COPYRIGHT: (C)2010,JPO&INPIT
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