Abstract: Apparatus for preventing a fire in electrical equipment when a relatively constant overvoltage condition appears on an input line comprises a meltable fuse in the line and a surge arrestor connected between the equipment side of the fuse and ground. The surge arrestor is physically located adjacent the fuse for melting the latter and open circuiting the line when the overvoltage condition is present for greater than a net prescribed time interval. In a preferred embodiment, the line adjacent the electrical equipment is a printed conductive line on one side of a circuit board, with the fuse comprising a gap in the printed line that is bridged with a bead of solder. The surge arrester is located under the solder bridge, with one of its leads extending through the board and connected to the printed conductor within the solder bridge.