TMOV34S Thermally Protected Varistor – Littelfuse
It consists of a 34mm square format varistor element ( MOV) with an integral thermally activated element designed to open in the event of overheating due to abnormal over-voltage, limited current conditions as outlined in UL1449. The device has a third lead, an indicator lead, which may be used to indicate that the MOV has been disconnected from the circuit.
The integrated configuration also offers lower inductance than most discreet solutions resulting in improved clamping performance to fast over voltage transients.