Device ID

We have a small WiFi net in our village that uses the Ayrmesh system hardware. The question is the names of the devices on the system. I have a utility that I can use to see how many devices, what their MAC addresses are and the name the user has given them or the mfgrs default name. Most of them are easy but a couple are bit strange. There are several devices that ID themselves simply as "U" and one that calls itself "repeater". I can guess that repeater is just that, a wi-fi repeater that anyone can buy. It's "U" that's stumping me. Anyone got a clue? I also have a couple that use HP or EK in their ID and I assume they are printers. Apparently some folks are using the net for networking their printers as well. Thanks,
Ron