Comment by jnewkirk

I had a pair of these transceivers when I was in my teens, from a somewhat later period, thanks to my grandfather who refurbished them from his time as a telegrapher at Western Union. Synchronization at startup took ten seconds or so while each unit adjusted its timing and apparently sent a correction signal to the other, drums whirling all the time and gradually matching initial positions. It looked like the most primitive process possible, but worked every time.