extending a telephone point

[Dave Liquorice]

Just shows how much you don't know then. You simply haven't worked on an old enough installation. There is a bit of "figure of 8" copper plated steel cored stuff still tacked along our soffit. Now as this place was derelict 30 years ago the original line must be younger than that. Our lines now come in on Dropwire No.10 though.

As to xDSL *requiring* a twisted pair no it doesn't, all it needs is a balance pair and an open line is balanced. Having said that the common mode rejection of an open line compared to twisted pair is going to be worse so the increased noise pickup will limit the speeds achievable by xDSL.

And I few years back I saw some open lines feeding several houses from a pole top. Can't for the life of me remember where. But they were most definitely open line, complete with double porcelain insulators each end etc. They don't install lines that reliable any more...

[Dave Liquorice]

Dropwire as used for the last 20+ years has been a round cable containing twisted pairs with steel strainers. See my other post, CW1378, Dropwire No.10 (2 pair) or No.11 (3 pair) IIRC.

Old drop wire was as you say a flat "figure of 8" single pair with copper plated steel cores.

[Andrew Mawson]

times,

black

figure

service

insulation

pairs

Yes, figure of eight configuration wire is the conventional way of describing two strands side by side each with circular insulation fused together to form (in cross section) a figure of eight shape. 'bell wire' by convention takes the same form.

AWEM

[Frank Erskine]

There's _still_ an extant one not far from here. Most of the drops are in dropwire, but feeding one house is a pair of 40lb wires on porcelain insulators - well, porcelain at the pole end and composition at the sub's end.

[Dave Liquorice]

"40lb wires" now that really will confuse the youngsters. B-)

[Tom]

Even in this day i need a fax machine and as all the computers are going to be out there i would also like the modem there.

Tom

[Tom]

I need to connect a modem, phone and fax machine and would rather wire something instead of having a unit in the house where little fingers can touch (15 month old!!!!) I have seen this:

item no 200026603229 in case the link doesn't work and looks like it will do the job. Any comments?

Thanks

Tom

[Andrew Mawson]

>>

> Ebay item no 200026603229 in case the link doesn't work and looks like it

Tom,

If it is any consolation I have had a 6 pair standard 'indoors type' bt cable buried in an 18" deep trench up my garden to my workshop for the past 15 years with no ill effects what so ever.

AWEM

[Dave Plowman (News)]

Right - I sort of assumed it was some sort of workshop.

However, if you're talking computers, the best way IMHO is to have the router/modem as close as possible to the incoming line and run CAT5 to the computers. CAT5 can also be used for an ordinary telephone circuit.

[The Natural Philosopher]

That is certainly my experience too.

Never seen that.

Not since maybe the late 50's possibly.

[The Natural Philosopher]

Ah...well maybe so. I was involved at the exchanges and with new install only. As far as the channel islands go I was installing Internet for te Tlecos, and the great rivalry between the islands as increased by the fact that whereas Guernsey had faithfully copied BT 'best practice' and installed thick copper twisted pair everywhere, Jersey has used thinner wire to save money, and had extreme issues with longer runs and ADSL..

There are also impedance issues. Its not probably an issue for a shirt run, but you need the characteristc impedance of twisted and a fairly constant 'power factor' over the total line lengthto get ADSL to work.

I don't think they are very reliable. Certainly when I first became aware of telephone lines in the early 80's standard practice was a steel cored twisted pair. I vaguely remember porcelain insulators on telephone lines in the 50';s tho. Our first phone was in the sixties, and IIRC that was installed with twisted pair and steel..not what you describe

I suspect that the porcelain and the figure 8 stuff was discontinued when system X took over. Its probably pre-war..

[Andrew Mawson]

Nope ! My figure of eight cable was installed post 1984 as it was installed while we have lived here and that's when we moved in. No porcelain insulators though, just a hook plate on the gutter board and a straining tail.

AWEM

[The Natural Philosopher]

Lord. Where ARE you? Outer Hebrides?

They must have had a few miles on some reels left over.

[Andy Wade]

No, the figure-of-8 stuff (Dropwire No. 6, I think) was in use well into the 80s. When I bought my first house in Cambridge (1979) I had to have a phone line installed and that was what was used.

In the late 50s I suspect you would have got two bare copper wires on moulded (not ceramic, by then) insulators.

ICBW but I associate the coming of the round 2-pair dropwire with the era when people started to have two lines - one for the phones and one for the modem.

[Andrew Mawson]

Well if SE London / NW Kent is in the outer Hebrides then yes

AWEM

[David Hansen]

On Tue, 19 Sep 2006 13:23:32 +0100 someone who may be Andy Wade wrote this:-

Indeed. I can recall it being installed around that time too.

Indeed. This is how it was explained to me by an employee of British Telecom at the time. They installed the stuff for two main reasons:

1) if there was a fault then there was a possibility that swapping the pairs would clear it rapidly and cheaply. 2) if one had a second line "installed" then they would connect up the second pair, but still charge you for installing a new line.

[Roland Perry]

In message , at 14:20:36 on Tue, 19 Sep 2006, David Hansen remarked:

Most of the cost of which was the exchange equipment, not the drop wire.

[David Hansen]

On Wed, 20 Sep 2006 21:20:15 +0100 someone who may be Roland Perry wrote this:-

Depending on circumstances that would be true in some/many cases.

[The Natural Philosopher]

Indeed. The wire coming into the house may or may not be anything from trivial, to many thousands of pounds..

I watched them pulling new cables up the road, and stopped to chat "Run out of pairs mate, some bugger up the road there wants a couple of extra lines, and we are having to upgrade 3 miles of cable so the bastard can get them"

Don't underastaimate what else has to happen on a new line install..wires have to be physically hooked up at the exchange, and the line tested end to end....hopefull VOIP will ultimately mean each exchange is simply an IP LAN wth 10Mbs connectivity for everyone, and off we will all go..Mmm. If video on demand takes off, make that 100mbps..

[Dave Liquorice]

But not the time if you had to fly and fix another completly new cable from the DP at the other end of the street or 4 fields away... Much easier and quicker to connect the spare pair at each end. B-)