In an addressable fire alarm system, in the loop wiring, a green/yellow wire(some people call it ground, other earth) is used. Why is it used. What's its role in the electrical circuit?

Thx

screen + fault use

screen + fault use

Could you elaborate on that, with some real life examples please? So I can once and for all understand the usage of this wire....

Thank you.

Edited September 28, 201114 yr by CerbNI

its a drain wire, not an earth

As above its not an protective earth and must not be grounded anywhere on the circuit except one end (usually) of the loop back at the panel.

Its purpose is to dump to earth all the noise the screen areound the fire cables collect to help stop interference affecting the data on the loop. It runs at low voltage (24-48v)