Abstract: A switch having an electronic trip unit and a power supply circuit for supplying energy to the electronic trip unit from a monitored circuit is provided. In the switch, the power supply circuit is formed by a linear regulator and a switching regulator. In this case, the linear regulator and the switching regulator are connected in parallel. The switching regulator has a Power Good output and the linear regulator has a Disable input, which are connected to one other. This arrangement requires little effort and, when a power supply is established, results in the output voltage being provided quickly by the linear regulator and the latter is then deactivated via the Disable input when the switching regulator, which operates with less loss, is able to provide the power supply. The switching regulator takes over the power supply automatically without any external additional elements or signalling.

Abstract: In an apparatus having a rotary switch which can be moved into a plurality of positions, each of which is assigned a different function of the apparatus, a different input signal is respectively supplied to a microcontroller when each position is assumed. In at least one embodiment, a firmware program accesses a table as external data source, the table directly assigning input signals and output values to one another, that is to say assigning the input signals to a switch position and assigning the switch position to an output value in one go.