PURPOSE: To suppress the current flowing to a closed loop between the windings, by turning on a switch circuit provided in the closed loop when no pulse signal exists, and turning off the switch circuit provided between the middle point of the winding and a voltage source.
CONSTITUTION: The switch circuits 26 and 27 plus the matched resistances 32 and 33 are provided to two closed loops respectively. A switch circuit 31 is set between the middle point of the winding of a transformer circuit 23 and a voltage source 25. When "0" of a bipolar signal is transmitted, both circuits 26 and 27 are closed with the circuit 31 opened. In this case the termination is carried out by the winding of the circuit 23 and the resistances 32 and 33 to realize the matching of impedance with the load ZL of a load circuit 24. At the same time, the supply of current to the closed loop is discontinued by opening the circuit 31. Thus the power consumption is reduced.
OOYAMA TETSUMASA
GOTOUDA TAKAO
TAKADA AKIHIKO
KOMIYA HISHIICHI
SASAGAWA MASAAKI
NIPPON TELEGRAPH & TELEPHONE