A communication unit or a vehicle has a control unit, a first connection, a second connection, a first switchable resistance bridge, a second switchable resistance bridge and a measuring apparatus for generating a measurement signal characterizing the voltage at the first resistance bridge. The first switchable resistance bridge and the second switchable resistance bridge are each provided between the first connection and the second connection and are connected in parallel with one another. The control unit has at least one first state and one second state, which first state corresponds to an active charging operation, and which second state occurs when the control unit in the first state receives an external abort signal via the first connection and the second connection. In the event of a change to the second state, the control unit turns off the first switch, turns off the second switch, and turns on the second switch.