| 摘要 |
A telecommunication line circuit includes line amplifiers LOAO and 1 which are connected to respective conductors TP and RG of a telecommunication line via feed resistances (R0, R1, Figure 1). A loop current measuring circuit SENC is coupled with the feed resistances and supplier signals to a resistance synthesis circuit LADC and impedance synthesis circuit LAAC the outputs of which are coupled back to the inputs of the line amplifiers. The resistance synthesis circuit is supplied with a signal VEET representative of line current by a circuit FDC (Figure 3) which has a controlled amplifier (OA4) and a resistance capacitance low-pass filter (R8, C1). The filter couples the measuring circuit to the controlled amplifier. Transistors (T3-T6) comprise a regulator which prevents sudden changes in the sensed line current from causing overshoot in the control signal (VEET) due to the time constant of the RC filter, by bypassing the resistor (R8) when the sensed current suddenly increases, and by short circuiting the capacitor when it suddenly decreases. <IMAGE> |
