Telegraphing your fist
Telegraph operators were known to each other by their "fists": The distinctive unconscious choices each made. Choices in how long they paused between a short and long beep, how they clumped letters together, and the overall speed of transmission.
That we can recognise each other in a literal series of beeps is a wonderment.
We learn who each other is from the tiniest unconscious choice and tiniest movements.