Unlike the regular shock baton, this weapon doesn't do shock damage. However, when it scores a critical strike, the target will fall to the ground. It does not depend on the use of V.A.T.S. for its knockdown effect, instead, it is triggered by every critical strike (though the stun only lasts for two seconds). Since it requires only 15 AP though, it is a good weapon to use with V.A.T.S.
Although it has a high base damage it does not do as much overall damage as the shock baton due to the lack of shock damage, but the knockdown effect does give an opportunity to deal a few more blows.
Enter the engine room during the generator-destruction phase of the main quest. Walk down the stairs and see a groove in the wall with a window. The weapon can be seen by looking through this window. Follow that corridor until it reaches the big open area. Take a sharp left upon getting to the open area, and then it will be the first left on the same wall. Go in that room and then follow the small corridor and at the end it will be lying on a table.
PCPlaystation 3Xbox 360 This weapon does not receive a bonus from the Xenotech Expert perk. [verified]
Playstation 3 In the Italian version of Fallout 3, the Electro-Suppressor will appear as "shock baton", making the game confuse it with the actual shock baton, thus making the Electro-Suppressor a regular shock baton. [verified]