Field device

A field device with a microprocessor and a display and/or operating module that can be disconnected from the field device, wherein the microprocessor controls the field device as well as the display and/or operating module, the microprocessor comprises an energy saving mode in which the display and/or operating module is switched off, wherein an energy supply of the display and/or operating module is interrupted during a transition by the microprocessor to the energy saving mode, further comprising a waking circuit which generates a waking signal when the display and/or operating module is connected to the field device, wherein the waking circuit comprises a comparator, a reference voltage and a measuring voltage are supplied to the comparator, the waking circuit comprises a measuring circuit at which the measuring voltage can be tapped, and connecting the display and/or operating module leads to a change of the measuring voltage that causes the generation of the waking signal by the comparator and wherein the measuring circuit is embodied as a second voltage splitter showing a serial circuit comprising a third resistance and a fourth resistance, with the third resistance and the fourth resistance being sized such that in a parallel connection of the fourth resistance and the switched-off display and operating modules the measuring voltage is equivalent to the reference voltage.