on 23/01/2018, Brian Gaff supposed :
Underground cables are the most difficult of course as there is no way to
find where the break is unless there is a tell tale crater in the ground
nearby of course!

Actually there is - They can send a pulse down a cable then measure the
time for the pulse to be reflected. Time = distance to fault.

It is commonly used on telephone cables too.

On 23/01/2018 17:55, Harry Bloomfield wrote:
on 23/01/2018, Brian Gaff supposed :
Underground cables are the most difficult of course as there is no way
to find where the break is unless there is a tell tale crater in the
ground nearby of course!

Actually there is - They can send a pulse down a cable then measure the
time for the pulse to be reflected. Time = distance to fault.

It is commonly used on telephone cables too.

Early ehernet transceivers had built in TDR circuits so you could find
faults. I don't know when they were phased out.

dennis@home wrote:

Early ehernet transceivers had built in TDR circuits so you could find
faults. I don't know when they were phased out.

I realise you're probably talking about thin/thick wire coax, but some
of the present-day Broadcom NICs have a driver mode that can tell cable
length, and a spectrum analysis of each of the four pairs.

On 23/01/18 21:54, dennis@home wrote:
On 23/01/2018 17:55, Harry Bloomfield wrote:
on 23/01/2018, Brian Gaff supposed :
Underground cables are the most difficult of course as there is no
way to find where the break is unless there is a tell tale crater in
the ground nearby of course!

Actually there is - They can send a pulse down a cable then measure
the time for the pulse to be reflected. Time = distance to fault.

It is commonly used on telephone cables too.

Early ehernet transceivers had built in TDR circuits so you could find
faults. I don't know when they were phased out.



I've got some servers that can estimate the cable length, so those
transceivers have something in them - but it may be a clever trick with
signal processing rather than dedicated TDR?