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I was very confused on how power was being supplied over RS-232 (DE-9). Apparently this is for Amiga's 9 pin connector which does have a +5V pin.

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I am not sure how it works on the amiga, but it was a common trick in the PC world to leach power off the DTR and RTS lines which idle at +12v and can provide a few ma of current per the RS-232 specs.

This is also why a lot of peripherals will fail when you use a knockoff 'rs-232' adapter that only outputs +-5v instead of +-12v

Rs232 says the signals only need to be +-3v minimum, so 5v is well within spec

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