The Voltmeter is an object in Mob of the Dead. It is used to activate certain objects around the map, such as Perk-a-Colas and doors. It can only be interacted when the player is in Afterlife Mode. The player must shock the voltmeter to overload it.
The Voltmeter is a replacement for the Power Switch that typically controls perks and other objects that require electricity. By shooting at it with electricity in Afterlife, it can activate and power up whatever it is attached to. The power is permanent with the exception of the Tower Trap voltmeter.
The Voltmeters also make an appearance in Shadows of Evil, which have the same purpose as in Mob of the Dead. The voltmeters must be shocked while in beast mode for them to turn on the Perk-a-Cola machines, as well as other utilities around the map.