Switching circuit for electrical devices of motor vehicles

Claim 1

A switching circuit for selectively operating a horn and one or more other electrical devices of a motor vehicle by manual operation of respective switches all of which are located on the steering wheel of the motor vehicle, comprising in combination: a constant voltage DC line; a first fixed resistance and a deviceselection circuit-assembly and an only slip ring contact disposed in the steering wheel hub, all the three in series and connected across the constant voltage DC line, said device-selection circuit-assembly comprising a plurality of parallelly connected circuits each of which is composed of a device selector manualswitch and a predetermined resistance connected in series therewith, the device selector manual switches all being disposed on the vehicle steering wheel; a horn circuit and at least one other electrical device circuit of the motor vehicle all connected in parallel and connected across said first fixed resistance; zener diode means in each of said other electrical device circuits of the motor vehicle to control power supply tHereto, the breakdown voltages of said zener diode means all being different, so that the electrical devices can be selectively operated all by means of the only slip ring contact, by breaking down the constant DC voltage in the line into a first voltage across one of said predetermined resistances and a second voltage which is suitable for conduction of the zener diode of the particular electrical device, the manual-switch of which is operated.