Ang mga bagong H.U ngayon usually have more than one power wire- an accessory power lead and a memory lead, some have a third wire for display illumination.

Heres what you need to know:
Dalawang option in connecting the accessory power lead: SWITCHED ( hot only when ignition is keyed) or UNSWITCHED (power is supplied all the time). Bihira ang H.U will remain illuminated, even when you turn them off, if the accessory power lead is hooked to UNSWITCHED power. Kaya mas magaling kung ang H.U ay naka hooked sa switched power so they wont drain your battery. Pero kung decide mo na gusto mong gamitin ito make sure to turn off your H.U when park your car or you risk draning your batt. Hehehehehe

You can get unswitched power from a direct connection to the positive battery terminal or from fuse that always hot. Be careful not to tie in to a circuit that could cause noise problems: usually any circuit that have a motor or switch somewhere in thier path.

The MEMORY lead must be connected to an UNSWITCHED source or the H.U memory will be lost every time the car is cut off. Most H.U wont operate w/o the memory lead connected.