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. - https://www.littelfuse.com/
TMOV34S Thermally Protected Varistor - Littelfuse
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.
Switching power supplies are power supplies switched by high-speed semiconductor switches. They are the most common type of compact, lightweight, high-efficiency power supply. Uninterruptible power systems (UPS) are backup power supplies that use a built-in battery to stably supply continuous clean power to connected devices when the regular supply power shuts down due to a power failure or other power problem. TDK-Lambda offers both these types of power supplies
Amplimo has got a very large range of toroidal transformers available directly from stock. Standard range transformers have been approved by KEMA and UL . Built and tested according to the international standard EN61558 .
They have two types, High Power Density for a large current discharge. High Energy Density for a long backup time. Over a million Charge/Discharge cycles. High Efficiency. Capable of fully discharging to zero volts.