Live Phone Lines?

DIYWell · 10 Oct 2016

I've a lot of old phone wiring in my building, some dating back to the 60s or earlier, some to the 90s. Is there any easy way to determine what wiring is in use and what isn't?

For instance, I've an old junction box in the basement but no idea where the wiring comes from. There a few working lines in the building, but I've no idea if they reappear here.

How would I test?

tally100 · 11 Oct 2016

If thats in the basement it could be the feed from the external DP ( distribution point) i would use a multimeter to check if there is 50v dc across the pairs

Lectrician · 12 Oct 2016

Looks like internal cabling from another internal DP. 20 pairs terminated from source, 5 pairs terminated on the far left top, extending onto somewhere else. Test for voltage on those.

jg321 · 12 Oct 2016

Lectrician said:
Looks like internal cabling from another internal DP. 20 pairs terminated from source, 5 pairs terminated on the far left top, extending onto somewhere else. Test for voltage on those.

Lectrician beat me, I was about to write exactly this!

Infidel · 15 Oct 2016

Another way but not always reliable is to look inside the lid usually if it is a main DP the exchange lines will be maked up with their number 6 digits or possibly 5 if an older installation, if it is a internal dp used for a pabx it may contain a mixture of Extensions off the pabx 2 ,3 ,or sometimes 4 digits + exchange lines for fax or alarms etc. But a multimeter set to 50 volts dc across the pair will tell you as mentioned above.

bernardgreen · 15 Oct 2016

You can identify which pairs serve which phones by picking up a phone which will then reduce the voltage on that pair from 50 down to about 9 volts.

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Live Phone Lines?

DIYWell

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tally100

Lectrician

jg321

Infidel

bernardgreen

DIYnot Local

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