I did some witring on an addressable system at a retirement home and used black / red as my loop, ( all was 3-conductor "FAS" cable) the only exception was where a single 5-conductor cable was used as a drop to a pullstation or smoke detector, the red / black pair was connected and deemed "FROM PANEL" and the blue / brown was connected deemed " TO PANEL" with the red/brown being Positive and the blue / black being the negitive conductors..
Not that it matters much but in this way with everything being uniform like that I could break the loop at any point while troubleshooting and know what pair was coming from the panel and what was going back to the panel..
A.D
