The Ecto Defibrillator is a medical device modified by Egon Spengler to revive ghosts with.
In order to reanimate Maiikrob, Egon retooled a Defibrillator to provide an electrical charge compatible with his ecto metabolism. Like a standard version, the charge is delivered via paddles. Most likely the device was set to deliver a certain charge based on the entity's frequency, as detected on the P.K.E. Meter and other measuring instruments.