Lee,

We call them drop cables but you may have a diiferet phrase in you area.

The velocity factor will depend on the type of cable it is. Your
description is not quite enough for me to identify it as we use
different cable types here in NZ.

If it's an overhead cable le with a soft plastic insulation (expanded
Pe) the velocity factor could be as high as 0.8. If it's harder
plastic - (expanded PP) the factor is likely to be a bit lower - 0.73
or so. If the cable is buried type Filled with grease it could be
lower still. If solid plastic insulation it is likely to be 0,67 or
thereabouts.

In the unlikey event it is PVC insulation, the velocity factor will be
lower again and also frequency dependent.

If you can get a sample of the cable to measure, then the capacitance
& velocity factor are closely related. Let me know the value & I'll
try & remember the equation..

RP

2009/11/7 Lee Jones <lee@frumble.claremont.edu>:
>> Can anyone give me the correct name to look for? I'm trying to
>> find the specs for those last-100m-or-so outdoor phone cables,
>> which are flat, single pair, but with a center support wire.
>
>> They have a very tough (black) plastic (very difficult to make knots).
>
> Assuming you are talking about overhead phone service --
>
> I've always known them as "drop cable" (since they provide the
> drop from the telephone pole to the premises). =A0It comes in both
> 1 pair and 2 pair versions with or without the carrier wire.
> The conductors, particularly in the version without a carrier
> wire, are steel. =A0About 20-22 gauge.
>
> I tried "steel wire drop cable" in Google and got a number of
> hits that seemed promising.
>
> If underground service, I believe standard UTP is used. =A0It used
> to be category 3 for phone service but it is likely to be cat 5
> now (just due to economy of scale).
>
>
>> I'm particularly interested in velocity factor (my ADSL is failing,
>> and the phone techs can't seem to locate the fault - or they don't
>> want to).
>
> Could be both! =A0(Incompetant & lazy are not mutually exclusive.)
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0Lee Jones
>
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