We needed to extend ethernet to the gate about 200 feet from the home near the gate for an access point, ip camera & doorstation. We only had 1 cat5 run to the area. There is NO local power in the area. We used a TP-Link 5 port gigabit poe switch and connected it to the cisco sg350 in the rack. Somehow the cisco provided the poe to power up the TP-Link and all the devices? How?

Give Georg Simon Ohm a call. He'll know the answer.

I tried calling but he wasn't home.

I believe Pakedge has a POE powered switch also.

That is weird, since TP-Link doesn't list that switch as being able to be powered by POE.
Did you stick your uplink connection into one of the 1 thru 4 ports?
Since those are suppose to be the POE ports and port 5 is the uplink port, supplying POE into one of those 4 ports might have reversed powered it?
There is a chance the switch might fail in the near future, since it wasn't designed to work that way.

You will want to use a 60 watt Poe injector to run 3 devices

[Link: blackwiredesigns.com]

How about 95 Watt?

[Link: planetechusa.com]

You need an analog phone to call him:-)

There are four pairs in the Cat5. The power from the Cisco (I'm assuming it's a PoE model) is traveling down the spare pairs on the Cat5. When they get to the TP-Link, and you plug the Cat5 into it, the TP-Link is now being back-fed power from the Cisco, as well as powering the other ports on the TP-Link (and therefore the devices connected to the TP-Link).

True or false: If you plug the wall wart into the TP-Link, 120 VAC will be present on the two prongs of the wall wart and you could be electrocuted!!

What spare pairs? It’s a Gb switch. All 4 pairs are used. (POE solves this by sending power and signal over the same wire. But there are no spares.)

This "Feature" isn't always advertised. I have run in to a few 5-8 port POE switches that can be powered via POE and pass POE even though the spec sheets make no mention of it.

We did plug the main feed into port 1, and then the IP camera & access point into ports 2 and 3. It's all working fine. Do you think we could have an issue down the road?

As long as you aren't pushing the limits on wattage I don't see why. And you stated that there is no local power so I'm not sure what you were planning on doing in the first place other than this type of a setup.

We were going to have local power installed. This was all done by the techs who did not understand and set it up and it worked by dumb luck. When we plugged it into the zyxel poe switch it did not work, so I'm guessing either it doesn't output enough power, or, the pins where the power are are in different locations and the TP-Link needs them in certain locations to power up the TP-Link switch.

I didn't see that it was a GB switch, however my answer is exactly the same. And I doubt any of the devices at the gate are GB devices anyways. But thanks for letting us know how smart you are when it comes to defining the various PoE standards! So very helpful to the conversation at hand.