Fusion pulse charge (Fallout 3)

The  is a device used to detonate the nuclear bomb in Megaton. It is given to you by Mr. Burke in Moriarty's Saloon. It is unknown how it works. The name might suggest it sends of some sort of pulse which activates a fusion reaction in the bomb and detonates it, resulting in a dirty bomb. The device appears to be very basic in its construction however.

Detonator
The Detonator is a World object in Fallout 3. Set up by Mr. Burke on Allistar Tenpenny's balcony, it's used in The Power of the Atom in order to activate the Fusion Pulse charge and detonate the Megaton bomb.