Electronic control circuit

Claim 1

A control circuit having an input, an output, a common and a control terminal for modifying an audio frequency signal applied to said input terminal in response to a control current applied to said control terminal and for applying the modified audio frequency signal to said output terminal, said control circuit comprising: first and second semiconductor diodes each having a cathode and an anode terminal, the cathode terminal of the first diode and the anode terminal of the second diode being connected to said common terminal, and the anode terminal of the first diode being connected to the cathode terminal of the second diode to form a junction; a resistor connected in a series circuit between said input and output terminals, said resistor being further connected in a second series circuit between said input terminal and said junction, said resistor and said diodes forming a voltage divider network between said input and output terminals; and a current limiting resistor connected to said control terminal and to said junction for applying dual polarity control current from the control terminal to said diodes to vary the impedance thereof in accordance with the magnitude of the control current applied thereto.