EdThomas wrote:Remember that I was a geography major but what about sound-powered phones.My peek at the Wiki article said they can be made to work up to 30 km which would be more than adequate for observer to battery comms. The hard part would be figuring out how to get the thing "invented" without going too far into the electricity swamp.
and of course they would be helpful aboard naval vessels.
From Wikipedia:
Operation
The microphone transducer converts sound pressure from a user's voice into a minute electric current, ...
No need to read further, the Proscription against electricity applies.