The Tesla Coil is a defensive block that, when activated, will electrocute mobs and players within a 4 block radius around itself. It will kill players without armor, and most mobs, with one hit (Endermen take 2 hits, Iron Golems require 4 hits). Even with leather or iron armor a player will die in two hits. With diamond armor they will die in four hits, unless they leave the 4 block radius of the Tesla Coil.
The Tesla Coil requires an IndustrialCraft power source and holds an internal charge of 5000 EU. Once charged, the Tesla Coil is on stand-by until activated. To activate it, apply a Redstone current. While activated, the Tesla Coil will drain 2 EU/t and will simultaneously target all mobs (including players) within a range of 4 blocks from the Tesla Coil. The electric shock will penetrate all walls and building materials, making it an extremely effective trap.
You must have a redstone input to turn it on. You can do this by placing a lever next to it or a redstone torch.