I am trying to identify this device, which I believe was used as part of a
cable-based system known as a Talking Rope, which was used by divers to
communicate with the surface.

I saw one of these systems last year. The whole thing was in working order,
but the stores codes were largely illegible and it was not possible to
borrow the equipment.

The overall system seems to contain several parts. First of all a headset
for the surface operator (I have a box of these in varying states of
completeness). I also have a couple of diecast boxes containing some kind of
potted amplifier, an on/off switch and space for a 9V battery.

Second, the Rope that goes between the two ends. The one I saw was bright
orange and the wires ran down the middle. I do not have one of these.

Finally, the microphone/earpiece which is goes under a diver's helmet and
rests against the skull, somewhere in the vicinity of the ear. This earpiece
is in a black plastic housing about 36 mm in diameter and 15 mm thick. It
has a screened lead with an inner conductor of 7/0.3mm (0.3 approximate).
The screen is a woven mixture of copper wire and fibre. The underside of the
earpiece has a clear plastic cover.

There is a stores code on the lead but it is not easy to read. My best
estimate of what it says is AP 0558/197925.

Can anybody identify the device or suggest a possible source of information?

Regards,
John Rabson G3PAI
Editor
Cave Radio and Electronics Journal