- A fuse is an over-surge protection device common among many electrical appliances, including homes and vehicles. Essentially, the fuse contains a series of wires that are rated to conduct only so much electrical voltage. Should the electricity passing through the fuse exceed that limit at any time, the fuse breaks, preventing the electricity from passing through to potentially do damage to your appliances, car or home. A plug fuse is a fuse designed for inclusion in a home fuse box. Such fuse boxes were commonly used before the invention of the circuit breaker. Most homes older than 50 years still have fuse boxes, and consequently replacement plug fuses are still sold in hardware and electrical supply stores.
- There are two types of plug fuse, both of which are compatible with the standard fuse box design pioneered by Thomas Edison. One is known as the Type T, while the other is known as the Type S fuse. The only difference between the two is the size of the plug at each fuse's base. The Type T is the standard size, almost identical to that of the common incandescent light bulb. The Type S fuse's base is about half the diameter of the Type T. This is to prevent accidentally plugging one fuse type into the wrong port in the fuse box, since the operational parameters of the two differ. If one fuse were to be placed into the wrong socket, it would play havoc with the electricity of a home, causing electrical appliances to short out. The Type S comes with an adapter that screws into place between the fuse box and the plug fuse, meaning the two types cannot be mistaken for one another.
- The housing of a plug fuse, be it Type T or Type S, is made the same way. It's a simple piece of conductive metal stamped to form a screw shape similar to that of a light bulb. The interior is hollow. Two metal leads extend from the inside to the center of the plug fuse. From the leads a ribbon of metal alloy extends through the center, closing the circuit. Depending on the operational parameters of the fuse, the exact proportions of the alloy as well as its size will differ. When the fuse is plugged into a fuse box, the ribbon will melt should electricity passing through the two leads exceed the given parameters, breaking the circuit.
