| 摘要 |
<p>PURPOSE:To connect a circuit to any terminal, by setting an input impedance of a subscriber circuit viewed from a subscriber line sufficiently higher and connecting an arbitrary impedance element to the subscriber line in parallel with said subscriber circuit. CONSTITUTION:Figure shows an example of a feeding circuit of a high input impedance subscriber circuit. High resistors 10, 11, 16, 17 provide a DC bias to the base of two transistors (TR) 12, 13 and set said TRs 12, 13 to a suitable active region. In this constitution, a DC resistor viewing this circuit between the subscriber line terminals 1 and 2 is a constant value. The bases of the two TRs 12, 13 are connected to a capacitor 18 to by-pass the AC component, allowing to set the input impedance of the circuit high viewed from the line terminals 1 and 2.</p> |
