Are BT overground cables supposed to be twisted ?

Are all above-ground cables supposed to be twisted pair ?

On the last couple of engineer visits, I've seen the cables that have been used. The first one was a piece of cable that ran between poles, and the engineer left me a piece that had been worn by rubbing against a neighbour's tree. This was a 12-core cable and none of the cables appears to be twisted. Recently, I had the drop-wire replaced between a pole and my house, and the engineer left some spare cable down the wall, so I could wire up an extension. This cable appears to be 4-core, with another 4 steel wires inside. Again, these do not appear to be twisted pair ?

Is there a reason why these are not twisted pair cables ?

It is twisted pair cable, but the pitch of the twist is less than you would expect to find with cat5/5e, When dealing with miles of the stuff, there is always a trade off, between interferance rejection, and the extra wire used in increased pitch cable.

Also take into account the cost of producing cable with more twists per unit length (at least, I think it increases the cost). That's why BT won't use cable that has a high density of twists - it probably costs more for them to run it, especially when you consider the fact that these cables run for miles rather than meters like CAT5. It's cheaper for them to use 'standard stuff'.

It is for this reason that ADSL was invented - to combat all the pitfalls of sending a signal over a long, unshielded, low twist density wire. FTTC is definitely the way forward, as is cable - because the only copper in those technologies is from your premises to the switch on the street, there after, fibre, which is not prone to the same interference as copper. I much prefer cable to ADSL any day because there is less room for errors to exist in the transmission medium, hence generally, it is much more reliable than ADSL and of course, faster.

Hope you get your line fixed soon zeb.

Thanks for the info, and for the good wishes

No more than the customers.

(Read that however you wish , but I wasn't impugning the customers).