Are telephone cables insulated?

[d000hg]

My house has a dedicated telephone wire strung about 100m up our drive. In one place it is hung off a bracket on a handy tree but in other I note it is resting (lightly) on a branch or two. There's no stress on the cable and I don't think these branches will grow in such a way as to cause any, but I am unsure if this will degrade the quality of service as I don't know if the cable is insulated.

Can anyone tell me? Keeping the wire free of serious obstruction is clearly something I (unless it's OpenReach's job?) have to keep on top of but how critical is it the wire is totally clear of the slightest contact with anything?

 

[rsgaz]

It will be 10b dropwire....

http://www.btcables.com/documents/CW1411-Dropwire-10B.pdf

The poly-ethylene outer jacket could be abraded by the branches over time, so you should keep them away, or water will get in, then the trouble will start!
They can take a fair amount of tension, because there are steel wires in there with the copper ones for exactly that purpose.

 

[Europlex]

10b dropwire

2 pairs, Green/Black & Orange/Brown

The Yellows are the Steel

 

[d000hg]

OK so in theory the cable can lie on the ground and still work, but I need to be wary of abrasion especially against a tree branch where there will be constant motion?

Presumably if it's a tree on my land, it's my responsibility? What happens if the cable should fray to the point of failure due to me not noticing a problem branch (it basically travels through a small wood and is quite hard to follow)?