My 45S head has two power inputs - one for the cooling fan, controlled from the white switch at the upper left - and one cable for switching/powering the lamp.
The white light lever is on the right side base. It disengages the filters from the light path; just moves them out or back to the dialled settings. It does not turn the lamp on or off. You need to use the timer for focus and exposure.
It does not have to be a timer, of course. A switched outlet would work.