Jaanus published a new build, a vocoder encoder relay board:
I designed couple of vocoder encoders. Vocoders are devices that encode sound by chopping it up by frequency bands and express each frequency band only by its amplitude. This kind of representation allows to mix all the frequency bands with each other. This have been used as a method of speech encryption in the past. I build one part of the system – relay board that took analog voltages and mixed them up with each other to provide encoding/decoding.
All source files are available at Github.