Sensor system for determining the properties of a transmission path between a transmitter and a receiver or for determining an object in the transmission path, wherein the sensor system is based on a feedback control, comprising - the transmitter, which is triggered with a transmission feed signal and transmits a transmission signal into the transmission path, - the receiver, which receives the transmission signal transmitted by the transmitter after passing through at least one part of the transmission path or passing through at least one part of the transmission path and being influenced by the object in the transmission path, and outputs a receiver output signal, - a compensation unit, which is fed with a compensation feed signal and generates a compensation signal superimposing the receiver output signal, - a processing unit for further processing the receiver output signal and generating a control value signal, - a signal generation unit, which generates the transmission feed signal or the compensation feed signal, and wherein the receiver is an Avalanche-Diode, characterized by - a reverse transformation unit, which performs a reverse transformation with the control value signal or a further processed control value signal, wherein - the reverse transformation is a transmission reverse transformation SRT and generates the transmission feed signal, when the compensation feed signal is generated in the signal generation unit, or - the reverse transformation is a compensation reverse transformation KRT and generates the compensation feed signal, which is fed into the compensation unit, when the signal generation unit generates the transmission feed signal, wherein - the control value signal is a measure for a property of the transmission path and/or the object in the transmission path, - the cutoff voltage of the Avalanche-Diode is modulated with the frequency of the feed signals (S3, S5) generated by the signal generation unit as modulation frequency. - the transmitter, which is triggered with a transmission feed signal and transmits a transmission signal into the transmission path, - the receiver, which receives the transmission signal transmitted by the transmitter after passing through at least one part of the transmission path or passing through at least one part of the transmission path and being influenced by the object in the transmission path, and outputs a receiver output signal, - a compensation unit, which is fed with a compensation feed signal and generates a compensation signal superimposing the receiver output signal, - a processing unit for further processing the receiver output signal and generating a control value signal, - a signal generation unit, which generates the transmission feed signal or the compensation feed signal, and - a reverse transformation unit, which performs a reverse transformation with the control value signal or a further processed control value signal, wherein - the reverse transformation is a transmission reverse transformation SRT and generates the transmission feed signal, when the compensation feed signal is generated in the signal generation unit, or - the reverse transformation is a compensation reverse transformation KRT and generates the compensation feed signal, which is fed into the compensation unit, when the signal generation unit generates the transmission feed signal, - the control value signal is a measure for a property of the transmission path and/or the object in the transmission path, - the cutoff voltage of the Avalanche-Diode is modulated with the frequency of the feed signals (S3, S5) generated by the signal generation unit as modulation frequency.