The Littelfuse TMOV34S thermally protected varistor series consists of a 34mm square format varistor element with an integral thermally activated element. This element is designed to open in the event of overheating due to abnormal overvoltage, limited current conditions. Certain TMOV34S devices are offered with a monitor lead which may be connected to signaling circuitry to indicate if the MOV has been disconnected from the circuit.