A sensor unit is disclosed with a safety system for use with a signal generator, where at least one evaluation unit is provided for evaluating a signal from a sensor and for producing a first trigger signal based on the signal. In at least one embodiment, a more compact and less expensive version of a sensor unit is provided, which operates reliably under high safety demands. In at least one embodiment, this is achieved by a safety system which has a checking unit for checking the operation of the evaluation unit using a test signal. The test signal is processed by the evaluation unit in the same way as the signal from the sensor. The two-channel output is provided on the basis of a conclusiveness check in the checking unit.