Some devices, such as servers and high-end switches have dual PSUs/power inputs, which can then be hooked up to separate UPSes, which are hooked up to separate power circuits (correct so far, right?).
However, many devices, such as standard switches, only have a single power input. This is problematic, because in a scenario where Circuit #1 fails, your servers might still be running off of Circuit #2, but your whole network infrastructure is down because it's also on Circuit #1.
How can power redundancy be set up for devices with only one power input (maybe via a power strip-type device with dual power inputs in itself)? Or would one have to specifically buy devices which are built with that capability in mind?