From what I understand, it used a sealed container with a liquid inside, which was used as a conductor for the signal and the sloshing of that liquid determined the strength of the signal passing out of the device. A motor controls the speed of the motion of the drum containing the liquid. I have no idea of how they controlled the depth, and I couldn’t find a schematic so I can only confidently state that it was a combined effort of the Bedrock Quarry and Spacely Sprockets.![]()
This would make it very similar to the old oil can echoes...