How to Connect a New RJ-45 Device to a Bus that is Using 1-4 Block Connection.

 A Lighting Control & Design bus that has been terminated with the 1-4 block connections do not use the 568B standard in the cat-5 cable and in most cases only use 3 pair from the cat-5 cable. You will typically run into 2 types of connection a single cable into a 1-4 block at a panel or end of line and 2 cables into a single 1-4 block at switches and other devices.

In each case the brown pair is not used; the blue pair is +12v; the orange pair is data and the green pair is ground.

To add a new device with RJ-45 terminals to a 1-4 block system you can use a Bus Checker card, a 1-4 Block to RJ-45 Converter or attach an RJ-45 terminal to the old cable using the correct color pattern NOT 568B.


To determine what pattern you need you need to understand how LC&D bus works.

With a bus using the 568B standard the following is what the colors conduct


With a bus using the 1-4 Block the following is what the colors conduct


To convert a 1-4 Block Bus:

  1. Cut the brown pair off.
  2. Green/White to #1
  3. Green to #2
  4. #3 Empty
  5. Orange to #4
  6. Orange/White to #5
  7. #6 Empty
  8. Blue/White to #7
  9. Blue to #8

The brown pair is cut off

The cable is now ready for a RJ-45 system.

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