Wiring standards

Standardising how wires are supposed to be connected is an effective method of increasing the maintainability and safety of systems.

AC power (Europe)

A good way to remember is that the brown lead shares colour with your underwear if you touch it. Blue can be likened to cold, analoguous to the negative in a balanced signal. Ground is not found in all installations. Of course, it is possible to swap live and neutral by just turning a plug around, so they should be treated with equal care.

DC power

RJ45 (ethernet)

RJ45 has two standards. Common for them is that they alternate striped and solid wires, starting with striped wires. The blue pair wires are always in the center, and enveloped by another colour. Brown is always the last colour. This leaves the green and yellow pairs as the only difference.

For a lone cable, the same standard should be used in both ends. It doesn’t really matter which standard is used. However, for wiring inside a building where connectors may be replaced in the future, it is important to make sure to consistently use the same standard to avoid creating crossover cables where not intended. T568-B is preferred if the A variant is not already in use.

T568-A

  1. Striped green + white
  2. Solid green
  3. Striped yellow + white
  4. Solid blue
  5. Striped blue + white
  6. Solid yellow
  7. Striped brown + white
  8. Solid brown

T568-B

  1. Striped yellow + white
  2. Solid yellow
  3. Striped green + white
  4. Solid blue
  5. Striped blue + white
  6. Solid green
  7. Striped brown + white
  8. Solid brown

Balanced audio

Balanced audio uses a positive signal, its negative opposite, and a ground. The colours used for positive and negative are usually red and blue, respectively. You can think of them as hot and cold. The ground is usually the bare copper sleeve.

Phantom power may be transmitted over the negative, usually as +48V DC.

TRS (tele jacks)

  1. Tip: positive
  2. Ring: negative
  3. Sleeve: ground

XLR

  1. Ground
  2. Positive
  3. Negative