Walk into a camera install from fifteen years ago and you will find two messes: the data cable that made the camera work, and a second, electrician-priced mess that gave the camera power. Half those runs were shortcuts, and the insurance file knows it.
Power over Ethernet settled that argument. The same Cat 6 cable that carries network traffic carries direct current to the device on the other end. Cameras, wireless access points, VoIP handsets, door strikes, clocks, small displays and access-control panels now install with one wire, one patch panel port, and one switch that budgets the whole thing.
The standards do the safety work. The switch and the device negotiate how much power the link may draw before anything energizes, so an unpowered legacy device or a dumb run of copper never gets shocked by accident. Categories matter for distance and heat, and this is where the cheap-install problem reappears: PoE budget is a physical property of wire length and gauge. Thin, long, badly terminated runs heat up and starve devices in ways that look like the camera failing and are really the cable failing, which is why a proper install starts with a load count: how many radios, how many cameras, how many phones, at what class, at what distance.
Then the switch and the UPS become part of the same design. When power drops, the access points, the cameras and the phones are exactly the systems that need to keep running, so the PoE switches go on conditioned power with the rest of the rack.
If your building still has cameras with local power bricks plugged into outlet strips, you are carrying the old mess. One cable does both now, and the building gets tidier, auditable and safer for it.