Seventy years ago this month, the October 1950 issue of Radio News carried the plans for this one-tube electronic keyer. The accompanying article describes the circuit in detail, but the reason for two relays is interesting.  The circuit uses a 117L7 tube, half as a rectifier, with the pentode section serving as the relay circuit.  The length of the dots and dashes is determined by the time constant (R times C) of the resistors and capacitors near the key.  Their voltage is fed to the grid of the tube, which turns the plate circuit on and off.

One of the critical design features is that the next dot or dash doesn’t begin until the previous one, and the space following, are finished. The second relay serves this function, as it doesn’t close until the dot or dash is completed.

The author of the article and designer of the circuit was Donovan V. Geppert, W5KFP, an Assistant Professor of Electronics at the University of Arkansas.  He was the author of the textbook Basic Electron Tubes, which is available online at this link.