What everyone has not mentioned, is that some newer appliances use lousy power conversion circuits to supply small chips for keyboards and timers. These chips are used as they and component displays are cheaper and more reliable over time, than their mechanical equivlent.
Some of these chips use the mains frequency or regulation . Others chips need relatively pure sine waves from the supply For various other things like zero volt switching..
Some of these chips use the mains frequency or regulation . Others chips need relatively pure sine waves from the supply For various other things like zero volt switching..