How can some electronics switch between 120v AC or 12v DC?

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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

7 Answers

Anonymous 0 Comments

Most electronic devices work on low voltages and DC instead of AC. The 120V is convenient for high power applications but it will absolutely fry any modern electronics. That is why in every household electronics device with a wall plug there will be a converter to reduce the voltage and make it DC.

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