Fuses have been used as essential safety devices from the early days of electrical engineering. This is a device that operates to provide overcurrent protection of an electrical circuit. Here is the 250V Glass Tube Fuse with the varying current. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby stopping or interrupting the current. Today there are thousands of different fuse designs that have specific current and voltage ratings, breaking capacity, and response times, depending on the application.