Radio unit with a power circuit for voltage supply and method for operating such a radio unit

A method for operating a radio unit for a plant of process automation, wherein the radio unit has a power circuit, by which an operating electronics of the radio unit is supplied with a first supply voltage and a field device connected to the radio unit is supplied with a second supply voltage, the method comprising the steps of:

• deriving the first and second supply voltages from a voltage source;
• the first supply voltage is tapped via a first connection of the power circuit and the second supply voltage is tapped via a second connection of the power circuit:
• and
• embodying said power circuit so that, upon interruption of a voltage supply via said voltage source, a second value of the first supply voltage is still tappable at the first output of said power circuit.

A radio unit for a plant of process automation technology, comprising:

• a voltage source;
• operating electronics;
• and a power circuit, which serves to derive first and second supply voltages from said voltage source, wherein:
• said power circuit has a first output, via which said first supply voltage is tappable to serve for driving said operating electronics of the radio unit;
• said power circuit has at least a second output, via which the second supply voltage is tappable to serve for driving at least one field device connectable to the second output;
• when a voltage supply via said voltage source is interrupted, a corresponding radio signal is emitted via a wireless communication interface of the radio unit;
• and
• said power circuit is so embodied that, upon interruption of said voltage supply via said voltage source, a second value of the first supply voltage is still tappable at the first output of said power circuit.