About STP/UTP cable, RJ45 connector and how to crimp RJ45 connector to Ethernet cable(STP/UTP)

This post is about ethernet cable. Standardized by IEEE 802.3 (Institute of Electrical and Electronics Engineers). First will explain the 8 pins on RJ45 (formal name is 8P8C as per IEEE which means 8Positions8Contacts), then different networking usage base on different wiring configurations and finally how to crimp the connector to cable. This ne

My cable:

2 types of wiring configurations: TIA/EIA 568B and TIA/EIA 568A.

EIA 568B wire lineup.

From the above pic, EIA 568B wire connection to RJ45 is:

  • Pin1 : orange/white
  • Pin2 : orange
  • Pin3 : green/white
  • Pin4 : blue
  • Pin5 : blue/white
  • Pin6 : green
  • Pin 7 : brown/white
  • Pin8 : brown

EIA 568A wire connection to RJ45 is:

  • Pin1 : green/white
  • Pin2 : green
  • Pin3 : orange/white
  • Pin4 : blue
  • Pin5 : blue/white
  • Pin6 : orange
  • Pin7 : brown/white
  • Pin8 : brown

3 types of cables:

  • Straight throught cable aka patch cable- For connecting different devices such as computer to switch, switch to modem.
  • Crossover cable – For connecting similar devices such as computer to computer, switch to switch.
  • Rollover cable aka Yost cable, cisco cable or console cable. Normally cable is flat to differentiate from the other cables. Use to connect computer to modem for technicians to perform network troubleshooting.

Pins 4,5,7,8 are use for power transmission, particularly for PoE devices like surveillance cameras or PoE LAN telephones.

Point to note that for Gigabit ethernet, pins 4,5,7,8 are also use to transmit data. So what if you have PoE devices that use Gigabit ethernet? The good thing is that Cat cables are able to carry data and power at the same time. This is due to the different frequencies, approx 50 million Hz for Gigabit ethernet and 60Hz for power.

Rollover cable ↑

Crimping of ethernet cable(Straight throught):

First stripped away about 2 inches of the outer insulation and untwist the 4 twisted pair. Straighten and separate all the 8 wires and arrange them in either 568A or 568B arrangement.

Roughly gauge how long is the crimp length by comparing with the RJ45 connector. The RJ45 back crimper must crimp on the insulation of the cable.