Voltage from electrical outlets fluctuates due to lightning, power plant generation issues, power line transmission issues and other factors. Surge protectors are vital to protecting electronic equipment from power surges and spikes. They slow down, block, or divert excess electrical power from reaching electronic equipment. These surges and spikes either immediately destroy or cause the eventual failure of electronic equipment. Surge protectors take the hit so that your TV and stereo don't have to. After all, it's far cheaper to replace a surge protector than replace your laptop. There are several types of surge protectors available, and they all use various technologies to protect equipment. Surge protectors typically have a neutral, hot/live and ground wire. One of the most common technologies used in surge protectors is Metal Oxide Varistor (MOV). These semi-conductors bridge the gap between the hot wire and ground wire in the protector. Under normal voltage conditions, the MOV has a large electrical resistance and does not allow much current to flow to ground. If there is a surge or spike in voltage, the MOV is designed to be electrically conductive and facilitate the flow of electricity to the ground wire, away from the protected equipment. Once the voltage level in the hot wire is reduced to an acceptable level, the MOV is no longer conductive. This prevents further current from flowing to ground, resuming its normal path through the hot wire. Gas discharge tubes are another popular type of surge protectors. These devices replace the MOV with a sealed tube of inert gas. Under normal voltage, the tube of gas is resistant to the flow of electricity. Once the voltage spikes to a sufficient level, the gas in the tube is ionized, causing it to be electrically conductive. This results in a flow of excess current from the hot wire to the ground. The current flow continues until the voltage level in the hot wire is back to normal. Other surge protectors are designed in such a way that instead of diverting electrical current, they have a circuit that slows and absorbs power surges. They then release the stored energy back to the circuit over the course of a few seconds. As a backup, many surge protectors have a fuse along the hot wire. This last line of defense is designed to transfer a certain amount of voltage. If the voltage level exceeds that which the resistor is designed for, electrical resistance causes it to heat up and burn the fuse. This breaks the circuit, stopping the flow of electricity. Surge protectors usually have a slight delay between the power surge or spike and the time the surge protector takes to respond. The longer it takes the surge protector to respond, the longer the connected equipment will be exposed to dangerously high voltage. By nature, power surges do not occur instantaneously; they take a few milliseconds to peak. This usually provides sufficient time for the surge protector to respond.