I have had a request from a group of cave divers for an alternative to a
conventional handset for this radio. An ordinary mike/loudspeaker setup is
not ideal when one has come up for air and is still wearing a full diving
outfit.

One of the divers has seen a bone microphone/loudspeaker which belongs to
Derbyshire Cave Rescue Organisation and wonders if it would be suitable for
use with the Heyphone. To check this out I need such a microphone, but
cannot borrow the Derbyshire one as to do so might compromise their
readiness.

The unit is known locally as a Talking Rope and is believed to be of army
surplus origin. I understand that it does appear to
have a stores code, but this is on a little rubber sheath on the cable and
is so perished as to be virtually indecipherable. The best guess is:- APP?78
147928 but the only certain reading is AP???8 ??79??.

Can anyone identified this unit please?

Regards,
John Rabson
Editor
Cave Radio and Electronics Journal