Evaluation of a coded switch position

The device has an encoder (3), a transmitter (4) and a decoder (5). With the switch closed an auxiliary voltage (U0) from the auxiliary voltage source (2) is applied to the encoder to supply it with energy, the encoder produces a pulse width modulated pulse sequence, whereby the on duration is a function of the auxiliary voltage and the transmitter transmits the sequence to the decoder. The decoder evaluates the pulse width modulated pulse sequence and determines a reconstructed value of the auxiliary voltage and is implemented in a component specially designed for decoding. Independent claims are also included for the following: a method of monitoring a switch position.