Another quick easy way if you're out in the field, lost your memory and have no wiring diagrams available.....just take a 4 pair jack (either 568A or B) and loop a piece of single pair cross connect wire from the blue to orange to green to brown pairs. Essentially, shorting all tips together and seperately shorting all rings together. You now have a loopback plug you can use at the smartjack or extended wiring. -CL