| 摘要 |
<p>Circuit device for a telephone set which includes an amplification circuit and voltage regulation element (10) inserted between a first and a second line end portion (11, 12), the said circuit element (10) including for its part at least one modulation terminal (LN), and a reference terminal (SL) to be coupled to the second line end portion which is taken as voltage reference, via at least one resistive element (9a, 9b) for measuring the line current, the said telephone set moreover including a line current regulation circuit comprising a first transistor (T1) able to introduce a voltage drop into the line loop.
<??>The principal current path of the first transistor (T1) is inserted between the first line end portion (11) and the modulation terminal (LN) of the regulation and amplification circuit element (10). It is controlled by a second transistor (T2) whose base receives the voltage developed on the resistive element for measuring current (9a, 9b), after filtering via a compensation diode (D), the junction point between the base of the second transistor (T2) and the diode (D) is supplied from the supply terminal (Vcc) via a current source (S1), and the emitter of the second transistor (T2) is connected to a threshold voltage source (30), (21a), (21b), of specified internal impedance.
<??>Application: telephone sets.
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