How to Make a RJ45 Cable Tester

Plug and Socket Wiring Details - T568A Standard:

NOTE: There are various wiring "standards". Some standards have different arrangements of colours. The basic configuration uses two pairs of wires ... Pair 1 - 2 and Pair 3 - 6. The other four wires are connected, but not used. In some standards, the wires in each active pair cross over.

(To find out about "Balanced Transmission Lines" see: http://www.brandrex.com.au/bptute.htm )

Also see: http://www.cabletron.com/support/techtips/tk0231-9.html - A great starting point for UTP CAT 5 wiring conventions. (NOTE: The diagrams are based on Standard T568B! The colour arrangement is different from the T568A Standard shown at the top of this page.)

Also see: http://www.netspec.com/helpdesk/wiredoc.html , http://www.techfest.com/networking/lan/ethernet.htm and http://www.engr.csulb.edu/~kwhittie/cecs572/gigabit.html

For an absolutely wonderful page on how to assemble RJ45 connectors see: http://www.lanshack.com/make-cat5E.asp

Crossover Cable - For connecting TWO (and only two) computers together. If possible use a different coloured cable, or mark it very clearly. If someone picks up your 'crossover' cable later and tries to use it as a conventional network cable, it won't work! Generally crossover cables are RED.

Crossover Cable
RJ-45 PIN	RJ-45 PIN
1 Rx+	3 Tx+
2 Rc-	6 Tx-
3 Tx+	1 Rc+
6 Tx-	2 Rc-

NOTE: A "crossover" cable is wired with T568A at one end and T568B at the other.

Rollover Cable -

A Rollover cable is used to connect between a computer and the "Console" port on a Router to allow programming of the Router. To make a rollover cable you arrange wires as per a standard patch lead of either type "A", or "B" with the jack on one end "rolled over". ie you turn the jack upside down and then insert the wires. (NOTE: you only 'flip' one end, not both!) Commercial rollover cables are usually made from flat cable to avoid confusion. If you cannot find flat cable you should use YELLOW cable when making rollover cables.

Wiring a Wall Plate -

From Wally Krueger ... if you look at an RJ45 wall plate (socket) from the back side the lower right wire is pin number 1. It then follows that pins 1,3,5, & 7 are on the bottom from right to left. The top row are pins 2,4,6, & 8. I wired my CAT5 cable to the wall plate using the same sequence as my straight through cable and everything works perfectly.

Wiring a Wall Jack -

A Simple Cable Tester

How it Works - The wires in CAT 5 Unshielded Twisted Pair (UTP 8-wire) are arranged in pairs. (Pin1/Pin2, Pin3/Pin6, Pin5/Pin4, Pin7/Pin8). The circuit below is designed so that when the ends of a UTP cable are plugged into each of the "RJ45 Sockets", the circuit for each pair is completed and the LEDs light up. If there is a break in a wire (or the leads are incorrectly terminated) the corresponding LED will not light. For remote testing (where you can't get at both ends) cut the board apart and plug the "terminator" section into one end and the "Tester" end into the other. - I haven't tested over how long a distance it will work. Good Luck!