| 摘要 |
A transistor T26, serving as an output circuit 42, has a collector connected to a communication line B+ and an emitter connected to the other communication line B-. A base current generation circuit 44 generates a base current Ib for actuating transistor T26 based on a transmission signal. Transistors T24 and T25 constitute a current-mirror circuit. A correction circuit 46 takes in or absorbs a current equivalent to base current Ib from the collector of transistor T26, so as to equalize the drive currents IB+ and IB- flowing through twin communication lines B+ and B-. Since only one transistor T26 is used to actuate the twin communication lines B+ and B-, it, becomes possible to completely equalize the drive currents IB+ and IB- in their absolute values and to cause no phase dislocation between these two drive currents IB+ and IB-. Hence, the radio noises can be completely canceled when generated from each of twin communication lines B+ and B- due to change of currents flowing therethrough.
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