Siemens Aktiengesellschaft

Karl Formanek

Franz Dielacher

Gerald Wallnberger

A step-down converter includes a self-conducting switching transistor (T ) and an inductance (L) located in a series arm, and a freewheeling diode (D ) located in a shunt arm. The switching transistor (T ) is controlled by a control transistor (T ). The control transistor supplies a blocking voltage, which is generated by a Zener diode (D ) in the series arm, to the switching transistor (T ) once a maximum value for a current (I ) in the series arm has been reached.

Step-down converter

In a method and configuration for forming a line termination at two line terminals of a telephone line, alternating signals are separated from direct signals applied to line terminals, referred to a reference variable and added to a transmission signal from a transmission terminal to form a resultant actual-value signal. The resultant actual-value signal is compared with a reference signal at a gain-controlled amplifier. The reference signal is formed with an impedance transmission function corresponding to a given termination impedance by weighting the alternating signal at one of the line terminals being connected to a current sensor resistor. A current between the line terminals is determined with a control transistor associated with the current sensor resistor. The control transistor is controlled with the gain-controlled amplifier.

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Vienna, Austria

Karl Formanek