On 06/01/2018 16:09, Brian Gaff wrote:
If they are the ones based on radioactive isotopes I believe you need to be
careful to make sure they get given to the right place.
If they use some other technology then its normally the council electrical
folk who send them for recycling.
I remember there was a bit of a stink when people dumped their old dial
trimfones. as the back lit figures were based on a beta lite ie a
radioactive gas in a sealed tube with a phosphor which the beta particles
stimulated and as the electron changed charge a pulse or photon was
emitted giving that eerie light. Brian


Quite a lot of old Trimphones were dumped in a skip on the Harwell site,
which got them a fine.

https://wikivisually.com/wiki/Trimphone

An audio specialist once claimed that the distinctive "Warble tone" was
perfectly optimised to make it difficult to locate.