Twisted Pair Cables — How Twisted?

[TicklyT]

Incidentally, the old grey or cream sheathed blue, orange, green, brown 4-wire internal telephone cables were laid up as one twisted quad instead of two twisted pairs, hence they were not recommended for carrying two lines.

The later white sheathed blue & white, orange & white internal cables had two twisted pairs. The outer sheath always looked uneven as the twists in the pairs didn't lay together nicely within the cable.

Most installations are now run using 3 or 4-pair cable. The outer sheath is not as smooth and round as the single quad stuff used to be, but it looks a lot better than the 2-pair cable ever could.

Some cables had a very slow twist - you'd have to strip back about 2 or 3 feet to stand any chance of pairing the conductors correctly if they weren't individually colour coded (in one colour coding system, one wire of each pair was plain white).
Once you started, you daren't let go of the free end of the cable, or the whole lot could unravel.

 

[Paul_C]

Incidentally, the old grey or cream sheathed blue, orange, green, brown 4-wire internal telephone cables were laid up as one twisted quad instead of two twisted pairs, hence they were not recommended for carrying two lines.

The green & brown in those cables were typically used for things like carrying a local earth to the phone if it was on a party line, and for providing the bell shunt and ringer connections where extensions were installed (at the time that cable was standard ringers were normally wired in series, not parallel like today).

(in one colour coding system, one wire of each pair was plain white).

And in one scheme all the wires were a single color and the pairing was the only way to identify them, e.g. pair 1 was plain white & plain blue, pair 2 was plain white & plain orange, pair 6 was plain red & plain blue, etc.