Daytime running light control unit for a vehicle and method to implement external lights as daytime running lights

The device controls at least one lighting device (3,5) depending on a readiness to drive condition by operating the lighting device(s) with reduced power. The lighting device is supplied with a pulsed supply voltage with a variable pulse width. The lighting devices include the headlamps and/or rear lights and/or license plate lights and/or fog lamps. AN Independent claim is also included for the following: a method of operating external lighting of a motor vehicle.