Visualizing how electronic signals work can be difficult. A physical model can be darn useful in overcoming that difficulty. At a recent workshop entitled “Unboxing Black Boxes” [Julian Hespenheide’s] group created a device to show Baudot Code in operation. This amalgam of wood and Arduino they dubbed émile in honor of Émile Baudot (1845-1903).
Baudot developed his code to transmit telegraph signals from one machine to another, in contrast to Morse code which was principally for human communication. Both codes were used throughout the 20th century. For example, those big clattering, mechanical teletype machines use a minor variation of Baudot code.
Baudot is a fixed length code of 5 bits, as opposed to Morse’s variable length code. Morse has a separate code for each characters while Baudot uses “shift’ codes to change between alphabet and figure characters. For instance, a binary 11 would represent either an ‘A’ or a ‘-‘ depending on the shift state. If the shift code was missed the receiver would get gibberish.
In émile the Baudot code is sent by marbles. That’s right, marbles. There are five marbles, one for each bit in the Baudot code. Each marble rolls in a track toward the Arduino. How does the machine know which marbles to send? “Punch cards”! These are a marvelous aspect of the design.
Each card represents a code. Each position in the card has a gap to allow a marble to pass ( a set bit), or no gap to block the marble (an unset bit). The operator loads 5 marbles and a punch card and launches the marbles via a spring mechanism.
[Julian’s] really created a great visualization of Baudot code with this project! Take a look at émile in action after the break.