SINGLE WIRE CAVE TELEPHONE SYSTEM
Many UK cave rescues
teams have used “Michie” type field telephones for many years with considerable
success, reliability and ease of use.
These phones run over kilometres of just a single wire, with the return audio
signal passing through the ground, and they have a runtime in days on Duracell
new handsets and 8 base stations were built in 2013 to replace ageing
equipment, some dating from the 1980s, and it has been issued to various rescue
teams. The latest design incorporates an
improved Michie type of audio circuit, together with new chips to provide
battery management, more features and control by software.
webpage is intended to document the project for anyone wanting to build sets
for themselves or to repair the 2013 sets.
The following links download zip files containing:
PowerPoint end-user guide and sound wav files [4MB]
PCB artwork and phone PIC software in MP-ASM [30KB]
CREG Journal article, circuit diagrams, bill of materials,
phone building guide [4MB]