An interesting and relatively thorough account of telegraph type technologies can be found in the early portions of James Gleick' "The Information", which I hig

An interesting and relatively thorough account of telegraph type technologies can be found in the early portions of James Gleick' "The Information", which I highly recommend. Spolier Alert: While the semaphore/flag telegraphs were a huge improvement in information speed and bandwidth in Europe, they were easily beatin on both points by "drum language" based communications along the Congo River, which predated telegraphs by some hundreds of years. The drum language was a code implemented by tapping on a sequence of high and low pitched drums in a manner that corresponded to the high and low tones of most of the (Bantu like?) dialects along the river. This isn't exactly binary since the timing of the beats mattered, but at any rate there would still be lots of ambiguity in mapping tone sequences to sentences. For example, in: (a) I have THREE pigs FOR SALE today (b) I know WHERE they HID YOUR cattle (a) and (b) can't be distinguished by their syllables and "tone" (designated by caps.) So There was a kind of hack that got implemented, where they would rephrase the message using semi-standardized groups of idioms. So you would have something like: (a) I have THREE pigs FOR SALE today (a) the FAT pigs numbering THREE FOR SALE on this nice day (a) THREE little piggies I have at my MARKET today and so on, until one has enough tonal and timing distinctness to map to a unique phrase. The message its self would naturally pass at the speed of sound, for maybe 1000 meters or so, before it had to be repeated, sometimes with the encoding changing at the boundary of different dialects. But apparently the repeating/encoding was rather efficient. https://en.wikipedia.org/wiki/Drums_in_communication#Drum_languages https://en.wikipedia.org/wiki/Drums_in_communication#Drum_la...