| 摘要 |
PROBLEM TO BE SOLVED: To provide a battery supply circuit having no transformer for a digital communication line. SOLUTION: This circuit shows a high impedance for a digital signal, shows a low impedance for a DC and limits a current for a constant voltage power supply. The circuit is provided wit a couple of control current sources having no transformer for each of lead wires (T, R) of lines. Each control current source is configured of a high gain transistor(TR) Q1, Q2 with a collector connected to a power supply (e.g. battery V1), with a base that is resistance-coupled with the power supply and capacitance-coupled with the corresponding lead wire and with an emitter coupled with the corresponding lead wire. Furthermore, the circuit is provided with a couple of control circuits for each current source. |
