Some are considered the inventor of the trigger MA Bonch-Bruevich, others - W. Ikkles and F. U. Jordan Anyway, all three had working samples, and this year the scheme turned 100 years old. Over the years, triggers have proliferated in huge quantities: only in the device from which you read this article, of course, they are no longer tube-based, more than people on the planet. Invented different types of triggers, differing in the number and purpose of inputs and outputs, the logic of work.
How to celebrate this anniversary? For example, erect a monument to the trigger. It does not require either granite or bronze, or a few square meters of space: it will take up very little space on your desk, but it will be valid. It is easy to purchase a finger double triode, and the assembly of the scheme takes about half an hour. But the author of IEEE Spectrum, Richard Brewster, decided
to complicate the task a little ...
He managed to buy two single UV201A triode for $ 35 apiece. They, of course, are not yet a hundred years old, but will soon be fulfilled. The design applied and resistors, made about the same time, but their authenticity had to be violated by placing modern ones inside them. In the initial state, they were very inaccurate, and getting a working trigger with them turned out to be problematic.
UV201A lamps are unusual: they have a direct glow, but its voltage is 6 V, like an indirect glow lamp. Incandescent indicator lamps also feed on the same voltage. A common power source for them was the battery of their four elements D, they are also 373, they are also R20. Sources of anode voltage and offset - respectively, +99 and -63 V - are from “crowns”. Old brass bell buttons allow you to apply +9 V to the grid of lamps to switch the trigger. The indicator lights are controlled by two vintage relays, the windings of which are included in the anode circuit of the triodes.
Well, it remains to slightly modify the scheme to record only the first press and did not react to the next ones (perhaps you collected one in childhood, only on MP transistors) - and the revived “Brain Ring” can be used at just in time.