One of my favorite podcasts, 99% Invisible, recently featured a story on the Bell Labs’ Voder and how its innovation lead to one of the best kept secrets in WWII high frequency communications: SIGSALY.

The episode is called Vox Ex Machina and, trust me, it’s a gem.

Stop whatever you’re doing today and listen to this brilliant little documentary.

I’ve embedded the SoundCloud audio of the episode above, but you can also listen via the 99 Percent Invisible website.