The
Bipolar encoding article would be an adequate, if short, subject item.
Yet it falls down badly on describing where bipolar signaling actually originated. Because we know exactly how it came into being. It was invented by William Thomson, Lord Kelvin, for use on the 1858 transatlantic telegraph cable. His "double-curb transmitter" device sent two pulses of opposite polarity, instead of a single polarity pulse, to cancel out the massive capacitance of the cable and allow a higher transmission speed.
https://collection.sciencemuseumgroup.o ... peripheral
The damn thing isn't even mentioned in the Lord Kelvin article. Except in passing.
https://en.wikipedia.org/wiki/Lord_Kelv ... ntic_cable
https://en.wikipedia.org/wiki/Automatic_curb_sender
That article has existed since 2009 yet almost no one looks at it. Tagged for lack of citations in 2009, what a nice bonus!
This is what happens when you let random people randomly write a "reference work". You get a partial picture of anything that isn't fanboy cruft. Obscure or not, bipolar signaling was an important development in telegraphy.