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.
The circuit was published in QST about 1981 and there have been a few newer versions come out over the years. This circuit uses a lot of discrete components but it has been very reliable.