Monoprice RJ11 and RJ45 Modular Plug Tester

Works as advertised, and useful to make sure you've got solid connections on your punch down keystones. Similar items are widely available and often also have BNC coax testers on them. So I cracked it open, and all of the traces are there for the coax connector. The local electronics store had the 1N4148 diode and square LEDs needed, as well as the coax jack. Soldering was easy as the holes were push-through, and already had solder on them. To make the coax terminator with an LED, use the appropriate connector for the end of the cable being tested and simply connect the positive LED lead to the center wire and the negative to the outside. Once you punch out the extra hole on the front of the plastic case of the Master unit (below the G light) it will light up the new LED in sequence.

This works great to verify that all wires are connected and working. It will show opens, mi-wired pins, and shorted pins or wires. It cannot test that the twisted pairs are mated to the correct pin pairs but this is a minor issue since that is easy to check visually. You can use 2 short jumpers to test your premise wiring.