Energizing a vacuum-tube flip-flop module from a 1948 IBM system
Summary
Ken Shirriff’s article deconstructs and demonstrates the TR-3 trigger module from the IBM 604, a vacuum-tube flip-flop built from dual-triode tubes. It explains how cross-coupled inverter pairs store state, the high-voltage and heater requirements of the 2033 dual-triode, and the challenges of level shifting, timing, and power supplies. The piece places the module in historical context, comparing it to earlier Eccles-Jordan trigger concepts and noting IBM’s later shift toward diode logic in subsequent machines.