Wanted: vacuum tube logic circuits

Chuck> Is the calculator article. Regarding other DIY, I remember a Chuck> morse- code typewriter that used microswitches as keys, but Chuck> not much else. I think it probabaly used diodes and relays. I don't remember relay based Morse code typewriters. Then again, there were the McElroy (and probably others) Morse code puched tape machines ("Wheatstone" code, two tracks) that were probably all mechanical, sort of like an ASR33 (but harder because of the variable length code). Somewhere in the late 1960s there were articles in QST showing electronic morse code keyboards. The first one I saw used ferrite rings as a combination ROM (like "rope memory") and shift register. The second one used ferrite rings as ROM but RTL logic ICs (Fairchild uL714, uL723) for the state machine. Diode ROM would be easy (it may have been done) and relays instead of RTL is also clearly possible but I don't remember seeing it. paul, ni1d