| 摘要 |
PROBLEM TO BE SOLVED: To make an equipment small in size and thin in thickness by inserting a semiconductor equivalent circuit to subscriber lines at a reference point and a U point with respect to an ISDN(integrated services digital network) line. SOLUTION: It is necessary to efficiently send a high frequency signal to a DSU(digital service unit) 12 through a high frequency transformer. At a U point, it is necessary that a DC component is cut by setting a signal component to a high impedance to allow only a high frequency signal component to pass through and that lines L1 and L2 are short-circuited for a test loop 2A from an exchange at the time of originating a call from a terminal. In this case, the resistance value is set to <=Ω812. A semiconductor equivalent L circuit 17 is inserted instead of a conventional RL filter, and then, heat generation is suppressed, and the equipment is made small-sized and thin, and further, a high filter effect is obtained.
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