@Bruce Brown posted:I had not seen this thread before, but @gunrunnerjohn's transistor circuit, evoked vivid nostalgic memories for me. It's called an astable multivibrator and was one of the first transistor projects I built in the late 1950's. (I may have also given away @gunrunnerjohn's age
) I may have seen the design in a Popular Electronics back then.
The astable multivibrator was first invented during WW1 by two French professors Henri Abraham and Eugene Bloch using the just-invented triode vacuum tube. Its application was to help precisely measure radio frequencies and used by the French, English and U.S. military. They both continued to make other advancements radio wave engineering in later years.
The Gestapo arrested Abraham in 1943 and Bloch in 1944. Both were murdered in the Auschwitz Concentration Camp.
Bruce,
Thanks for the History lesson! Very fascinating. Sad ending, unfortunately.
As for the theory, I took an IC design class in college and I remember learning about this! That's where I pulled this from when I came up with the design. This theory is very elegant. Abraham and Bloch did tremendous work. I have an electronics textbook that outlined this and it made the most sense. There's also the mono-stable (one stable state) and bi-stable (two stable states) multivibrators. They are used all over today. The astable multivibrator means there is no stable state, so it oscillates. I remember learning how to design clock generators and oscillators with this theory in mind.
The simplicity of this design is its greatest asset 
Thanks for the trip down memory lane back to EE school!
