I get an used Aristo cold light head for Beseler 23C from a flee market unfortunately without any instruction leaflet...

The head is composed of 2 parts: the head itself and a powerpack unit. Each has an electrical 3 prong cord to connect.
So, I wonder which is the right way for connecting :
a) connecting head to AC outlet and powerpack to timer?
b) connecting head to timer and powerpack to AC outlet?

Thank you for your answer(s).