This is a my old faithful keyer. I originally built this keyer in 1981 and I reinstalled the electronics in a much better enclosure in 1995. The keyer features 8 memories, auto spacing, adjustable speed & weighting, separate paddle and key inputs, beacon mode, positive or negative keying, fuse, extremely low power requirements, and a bullet proof housing. There is no power switch due to the very low current requirements and I only have to replace the four AA batteries about every four years or so.
The original circuit was written up in the October 1981 issue of QST by Jeffrey D. Russell, KC0Q and there have been a few newer versions come out over the years. I'm using the original circuit and it has been very reliable even though it uses a lot of discrete components.