An electronic circuit that changes a charge signal into a voltage signal within a sensor suitable for direct installation in a roadway can be connected to two single-core cables that need not be highly insulating yet can realize the required power supply of the electronics. The circuit includes an integrated impedance converter (IEPE) at the output to a two-core cable and a charge amplifier with an IC1 that has two inputs. A capacitor Cc is connected in series to the signal output of the sensor at one input of the IC1. A Zener diode D is arranged between the ground output of the sensor and the second input of the IC1 and can be supplied with power by a resistor R1 in conjunction with a power supply arranged on the output side in order to adapt the potential at the second input of the IC1.