In most wire communication systems, communication lines are also used as power lines. Therefore, the powered terminal needs to separate as communication signals and dc supply power in its input Well-known separators usually utilize a combined circuit of inductors (or transformers) and capacitors. When the lowest frequency of the signal is low, the inductance bocomes high and the size of the inductor increases. A conventional electronic choke circuit with no inductor has the disadvantages that power dissipation is high and the dc current is limited to unidirectional flow. Our original communication system consists of low-power dc-dc converters. Because a converter in the powering terminal operates not only as power supply but also as transmitter, it is preferable that the electronic choke be bidirectional. In this paper, the ac voltage attenuation characteristics of a new low-loss electronic choke with small inductors and an amplifier are investigated by experiment and analysis.