Reminds me of an interesting Great War technology. During WW1 the British used a system called the "power buzzer" which used two spaced electrodes and sent an a

Reminds me of an interesting Great War technology. During WW1 the British used a system called the "power buzzer" which used two spaced electrodes and sent an alternating current through the earth. Apparently this could be picked up and amplified by another ground electrode at some distance, and was used to send morse code communications. I'm struggling to find a good modern explanation but here is a scan of the original military manual: https://cgsc.contentdm.oclc.org/digital/collection/p4013coll9/id/255 https://cgsc.contentdm.oclc.org/digital/collection/p4013coll...