These are not shown in the previous table. They will be introduced later in this text.įor the wires left, the "even wires", there's only one color. The question marks (?) were put there because these pins will have different colors in the two standards. Odd wires always have White + some color. If you have to memorize, first try to remember this fact. (Abbreviations: G=Green, O=Orange, W=White, Bl=Blue, Br=Brown)Īs we can see, "odd wires" (cables whose position is an odd number) always have two colors, that is, White + Green/Orange/Blue/Brown. The definitive answer is from the 802.3 specs. So, let's take this, as it's the first thing in common between both standards. That said, per the IEEE 802.3 specs, in a Gigabit Ethernet crossover cable, the pair at pins 4,5 is crossed with the pair at pins 7, 8. Some have just one color, and others have a color together with white. If you terminate RJ45 jacks at both ends with different TIA/EIA 568 standards (one side TIA/EIA 568A and other side TIA/EIA 568B) you will get a Crossover cable.įirst of all, we know that UTP cabling is composed of 8 wires, grouped in 4 pairs. This cable can be used to connect two DDS CSU/DSU (i.e., DSU) products in a back-to-back configuration.If you terminate the RJ45 jacks at both ends of a patch cable with same standard (either TIA/EIA 568A on both sides or TIA/EIA 568B on both sides), you will get a Straight-through cable. This pinout is the same for both a RJ-45 plug and RJ-45 jack.įigure 5 shows the pinout for building a DDS crossover cable. This cable can be used to connect two T1 CSU/DSU (i.e.,TSU) products in a back-to-back configuration.įigure 4 shows the pinout for building a DDS loopback adapter. This pinout is the same for both a RJ-45 plug and RJ-45 jack.įigure 3 shows the pinout for building a T1 crossover cable. The first (far left) colored wire (pin 1) at one end of the cable is the third colored wire (pin 3) at the other end of the cable.
Hold the cables side-by-side with the tab at the back. There are eight pins total in a RJ-45 connector.įigure 2 shows the pinout for building a T1 loopback adapter. You can identify a cross over cable by comparing the two modular ends of the cable. This document shows the necessary pinout for building them.įigure 1 shows a how to orient a standard RJ-45 to RJ-45 silver satin cable to determine pin 1.
Loopback adapters and crossover cables are useful tools for troubleshooting both DDS & T1 circuits. Loopback Adapters and Crossover Cables for T1 and DDS Circuits
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