Electronic ring counters are the counterpart of mechanical counter wheels. Relays driving the counter wheels are replaced by vacuuum tubes (also named thermionic valves). The concept is developed by Eckert and Mauchly in the ENIAC, the first electronic computer operational in 1945 and completed in 1946. The use of electronic techniques increased operating speed enormously.
Like counter wheels, numbers are stored in decimal form. The ring counter contains 10 vacuum tubes, one of which conducts current at any time. Pulses enable the next vacuum tube to become active. In this way the unit counts pulses from 0 to 9, indicating a carry when it switches from 9 to 0.
The ENIAC had in total 20 accumulators consisting of 10 such ring counters.
The use of termionic tubes as switching elements became common practice in early computers. In 1950 Eckert and Mauchly build the UNIVAC, the first commercial computer in the US. They started their own company, the Eckert-Mauchly Computer Corporation, later on acquired by Remington Rand.
The unit shown, holding ten gas-filled 2050 triode tubes, is a decimal ring counter as used in the first Univac computer. It connects to the computer's circuitry by means of 26 silvered conical 'pins'.