What is presented is a control device for a multi-voltage on-board electrical system of a vehicle, wherein the multi-voltage on-board electrical system has a first electrical subsystem, which is configured to be operated with a first supply voltage from a first voltage supply source, and a second electrical subsystem, which is configured to be operated with a second supply voltage from a second voltage supply source. The control device comprises: a transceiver, which is connected to ground via a first ground terminal of the first electrical subsystem and which is configured for communicating with a communication component of the first electrical subsystem; a control unit, which is connected to the same ground via a second ground terminal of the second electrical subsystem and which is configured for controlling a power component of the second electrical subsystem; a transmission path, which couples a signal output of the control unit to a signal input of the transceiver, wherein the transmission path is configured for transmitting a control signal provided by the control unit at the signal output towards the signal input of the transceiver; a diode arranged in the transmission path, the cathode terminal of said diode being coupled to the second ground terminal. Provision is furthermore made of a number of field effect transistors, wherein the number of field effect transistors on the one hand couples the transmission path to the first voltage supply source and/or to the second voltage supply source and on the other hand couples said transmission path to the first ground terminal and/or to the second ground terminal.