A small point worth noting. A drop wire (or drop cable) is an aerial feed. An underground cable is best described as a service feed (cable).
Both CW1417 and CW1420 specification cable use --
- Pair 1 Orange/White
- Pair 2 Green/Black
- Pair 3 Red/Grey
- Pair 4 Blue/Brown
Slight amendment .............. Green/Black is the last pair when working on these cables. This kind of colour coding pair-count (although now seen in the newer cables), is actually a throwback to the old-style
'Concentric cables'.
It matters not what the size of the cable ...... Orange/White is always PR1, followed by Red/Slate, then Blue/Brown, then Red/Slate, Blue/Brown .......................................................... until you get to the last pair (marker), which is Green/Black.
It is a quality failure should an auditor spot an engineer has used the Green/Black as PR2 instead of Red/Slate.
To the OP ............. as mooted above by many, the telephony systems of today are not polarity conscious, but there are still odds and sods of kit out there that require it to be so ........... old business systems, some pay-phones and also 'Caller Display Units' have all had us scratching our head at one time or another.