If you repaired televisions in the 70s, most of the IBM 604 trigger circuit looks completely ordinary: a couple of triodes, plate resistors, grid bias, coupling

If you repaired televisions in the 70s, most of the IBM 604 trigger circuit looks completely ordinary: a couple of triodes, plate resistors, grid bias, coupling capacitors, and voltages high enough that you kept one hand in your pocket. Shirriff's observation that the trigger can oscillate, latch wrong, or refuse to switch unless the voltages are just right is especially familiar. We used to call that "the set’s acting up"; computer people called it logic margins. The later diode-controlled version is revealing too. Engineers weren’t escaping analog electronics so much as steadily boxing it in until the analog behavior became somebody else's problem. Early digital hardware makes a lot more sense if you approach it with a voltmeter instead of a truth table.