https://www.youtube.com/watch?v=ug5lUI-hs3s

This video shows a Baudot teletype machine and he explains the basic principles well. It also operates and he shows you how the electromagnet converts the signal pulses to a letter selection via linkages.

You can also hear how fast the signal is as it's running. No way a human operator could tap that out. The first few decades of telegraphy were human controlled, hence why Morse's code was popular since it was tailored for human abilities. Once telegraphy got established, lines were run and the technology was generating money you start to see automatic machines come around to speed things up.

The first automatic machines worked by punching the code out on a paper ribbon first, then you ran that message through a special telegraphy key. This allowed Morse code to be sent as fast as possible. Registers were common place since the beginning so recording the signal to be decoded to english was simple. This was the era of "battery rooms", since it was all DC powered and a proper DC generator hadn't come around yet. Also the era of rooms filled with operators, often women, coding messages into punch-card-ribbons to be sent and decoding register ribbon into english.

Post Civil War we see all of this mature into new coding methods, multiplexing (where Edison made his first fortune), binary transmission systems like Baudot code and eventually transmission of voice. Ironically, Alexander Graham Bell was working on a multiplexing telegraph device (harmonic telegraph that used 4 tuned forks to send multiple codes of various frequency that 4 tuned receiver forks could receive independently of each other across a single line) when he figured out voice could be sent.

One of these tuning forks metal reed had become struck to the electromagnet and Watson plucked it free. Bell, in another room, heard his devices corresponding fork undulate when it was plucked free. He didn't hear the solid pulse you'd normally hear, he heard it undulate. Bell had studied hearing his whole life (his wife was deaf) so he understood immediately when he heard the undulation that sound could be sent electrically. So he gave up the harmonic telegraph (which didn't work well because tuning forks were finicky as hell--it wouldn't be until vacuum tubes came around that it became practical) and started working on the telephone.

Lots of fun history. A distinct period of innovation in the broader Industrial Revolution. When a guy who could understand mechanical movements could invent something that'd make him like $800,000.