A deep dive into the TR-3 trigger module from the 1948 IBM 604 Electronic Calculating Punch, one of the first programmable calculators using vacuum tubes. The post covers how vacuum tube triodes work, how two inverters form a flip-flop (trigger) circuit, the reverse-engineered schematic of the TR-3 module, and a live demonstration powering the module. Historical context traces the flip-flop from the 1918 Eccles-Jordan circuit through ENIAC and IBM's BCD decimal counter patent to modern transistor-based flip-flops used by the millions in today's CPUs.
Table of contents
How a vacuum tube worksInverters and the trigger circuitConclusionNotes and references80 Impressions