Circuit for electronically generating a call impedance

A circuit arrangement for electrically generating a ringing impedance in a telephone terminal, the circuit arrangement comprising:

• a plurality of transistors, the ringing impedance being adaptable by controlling a resistance of a first transistor;
• a first capacitor;
• and
• a first input terminal and a second input terminal, the circuit arrangement having a ringing alternating voltage which can be tapped between the first input terminal and the second input terminal;
• wherein a digital controller having a programmable digital filter sets the ringing impedance according to predetermined conditions by generating, from the ringing alternating voltage, a control voltage for controlling the first transistor;
• wherein a transmission function of the programmable digital filter can be set by programming filter coefficients;
• wherein a second capacitor, a load path of a second transistor and a first resistor are arranged in series between the first input terminal and a reference potential,
• wherein a third capacitor, a load path of a third transistor and a second resistor are arranged in series between the second input terminal and the reference potential,
• wherein a first input potential and a second input potential of the ringing alternating voltage are fed to the digital controller, and
• wherein the digital controller provides a first control voltage for driving the second transistor and a second control voltage for driving the third transistor.