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!!