This is an RJ45 cable tester, which recognizes particular kinds of cable (Ethernet, rolled, Ethernet economizers, audio cables), both 4-wire and 8-wire. If you only ever need to test a few single cables a year, you won’t need this. However if you’re trying to test more than one cable at a time, particularly if they are long runs or hidden, this is great. Normally Ethernet testers come in remote/master pairs, so you have to
– go to remote site (attic, patching closet, whatever)
– attach remote terminator
– go to local end
Rinse, lather, repeat. One trip per cable.
The nice thing about this tester is that with the numbered terminators, you can test several lines at a time, without having to dash up to the attic each time to change the remote terminator. You can also see easily when you’ve mislabeled cables. (“Patch panel port 2 has terminator 8 on it? Bugger. Time to re-label…”) It’s also useful when you have a mixed bag of cables which you need to identify and sort into boxes. As a network engineer, this is something I have to do quite often…unfortunately.
Oh, and one other thing — if you switch it on without a terminator, it will show you how to wire Ethernet patch and crossover cables, including the cable colors. It’s kinda shiny. Yes, it’s more expensive than the kind you get for cheap off Ebay, but it also does so much more.