[TSoC] [UPS, USB, X10] X10 UPS and USB power supplies.

Observations:
* X10 was once used to allow remote control of power outlets. It operated by adding a small set of pulsed high-frequency modulations on top of your home's internal AC. Take a peek at it with an oscilloscope some time; it's pretty cool.
* UPS devices report themselves well over USB, but that takes up one of a computer's external USB ports.
* In most systems I've seen and built, there are spare USB headers left on the board after building a system.

Proposal:
Taking these three in context, consider having a UPS self-report its status by doing a controlled modulation of its AC output. Have a computer's power supply be capable of receiving and interpreting these signals. Have that power supply plug into a spare USB header on the motherboard, to provide those communications onward to the system.

Benefits:
* Avoid using an external USB port
* Allow multiple computers powered off of the same UPS to be simultaneously aware of their power source's state.

Drawbacks:
* AC output of UPS can't be a perfect sine wave, much as that would be ideal. (Though most output a stepped approximation, anyway.)
* Requires that the PC's power supply be able to interpret the signals.


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:wq