Safe input circuit with one-channel peripheral connection for the input of a bus participant

Comparison circuit for a signal input circuit of an input component with a one-channel periphery connection for the connection of at least one signal generator, where the signal input circuit (110) for reading input signals applied to the input component is connected electrically to an evaluation circuit (120) via a first coupling element (IC1), the comparison circuit comprising:

• a reference voltage source comprising a reference diode, wherein the reference voltage source is for providing a reference voltage for the activation and deactivation of the first coupling element;
• and
• a test circuit for testing the reference voltage source and comprising two voltage dividers, which are constructed from three resistors and are connected to the reference diode, for setting the reference voltage;
• wherein each of the voltage dividers is connected to a corresponding second coupling element for the corresponding individual superposition of a current flow.