<p>The safety sensor (1) has a switching contact (2) that is opened or closed by an influencing element. The test signals generated by a signal generator (3) are transmitted through the switch contact and applied to a switching stage. The superposition of switching signal generated by test signals is detected to generate output signals. The output signals are fed to a signal decoder (5) and the switching signal is recovered. The switching signal and dynamic checksum output consisting of outputs of switching stage and test signals are output.</p>
