For example, I have an antique portable television made by the Singer manufacturing company that plugs into US mains. However, it also has a 12v DC input and can run off of that. I also have a retro CCTV monitor that uses the same 120v mains plug and has a placard on the back that says it can use a 12V 12W battery. How is this possible? If an electronic device is designed to take 12v, wouldn’t 120v destroy the device? On the other hand, if a device is designed to accept 120v, shouldn’t 12v not be enough to operate it?
Edit: added a clarifying question
In: Physics
Internally, the devices have ‘stuff’ which reduces 120v to 12v, and the device uses these and runs off 12v if you plug 120v into it.
If you plug 12v in, you connect directly to the internals without going through the ‘stuff’, and it runs off that 12v.
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