The electric illuminator is powered by two AA size batteries. It utilizes the standard but unusual flat disc-shaped McArthur bulbs. The battery compartment cover is also the on-off switch; sliding it to allow a piece of insulating material to contact one of the batteries will turn the unit off. There is a built in condensing lens, and a diffuser screen which can be slid in or out as desired. Compared to earlier models, this illuminator is heavier and rectangular; the diffuser screen was supplied with earlier illuminators such as the Cooke-McArthur, but my earlier Cooke-McArthur example does not have one; it was apparently supplied as a separate accessory, whereas in the Kirk example, it is built in to the illuminator.