A transformer tap changer is an in-built mechanism which allows for variable turn ratios to be selected that changes the ratio of the primary to the secondary winding. Tap changers in transformers involve protection and control schemes and one of them is to sense if the tap changer assembly is in odd or even position. This is to ensure that the no load taps and operated before the taps carrying a load. A magnet or a set of magnets mounted on the moving assembly arms are used to trigger a Reed Switch mounted on the transformer. Since this assembly will be located inside the oil tank of the transformer, special Reed Switches capable of withstanding high temperatures are used. Suitable products: HW-5052 reed switches and HW-5052 reed switch based sensors having a higher operating temperature range.