phone light problem

OK, well it's thicker plastic and completely waterproof. - I'm not sure conduit is.

What is a code violation now might not have been 24 years ago and code is not retrospective.

It's not conduit, it's a cable duct - we had loads between and in buildings at work, though I admit they were all salt glaze pipe.

Codes and wiring regulations are all about safety. Codes lay down specific measures and standards under given situations but there are also situations which they do not exactly match and decisions have to made. OK, perhaps they do cover this situation but I'm still going to use my own common sense and make my own decision.

In this situation the important things are that the cable is rated according to the load and appropriate overload protection provided - it is.

The cable must be protected from mechanical damage and effects of attack or corrosion by water in the soil - it is

Whether or not it meets code, current or historic I consider the above requirements to have been met I'm certainly not going to try a dig it all up now.

If I was doing it again now then of course different considerations would apply - particularly the ridiculous Part P of the building regulation.

as I unserstand it lowest resistance you're allowd while on-hook is 1M per phone, that'll pass 48 microamps which won't light a LEd visibly during the day, and may not at night either.

probably the easies way to do it is to use an external power soure and and extra wire to power the LEDs

There is undoubtedly equivalent regulation there. Suck it up.

?-)

Yes I did have a copy of the regs that were in force at the time but where that is now I have no idea and, of course, they've changed things since then and issued new versions.

When we bought this house about 30 years ago, the electrics needed a fair bit of work. I bought the regs, read and followed them while I did the work, and haven't done anything since, so I didn't need to buy the later copies.

where

fair

Well the way things usually work, you took the option to upgrade to then current standards when you bought the place. If i understand grandfathering right in this case, you do not have to exceed the = standards you used in the upgrade if it would impose undue costs. The tricky item here is "undue costs".

?-)