Ninety years ago, the January 1926 issue of Popular Mechanics showed this simple but ingenious device for practicing code. It allowed the aspiring radio operator a way to generate perfect code with a buzzer.

The board (preferably oak or ash) had a series of grooves.  At the beginning and end of each dot and dash a hole was drilled.  Copper wire was threaded up through the holes, forming a conductive path for each letter.  The other contact was slid over the letter at any desired speed, forming perfect code.

The article noted that a similar device had been used in the early days of the telegraph, presumably allowing unskilled operators to send (but not receive) messages.

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