Remington Rand / Eckert-Mauchly ring counter
UvA Computer Museum catalogue nr 03.02
The unit was connected to the computer's circuitry by means of 26 silvered conical 'pins'. Its length is 59.7 cm.
The lower image shows a number of more recent decimal ring counters; all have about the same functionality as the Eckert-Mauchly counter but are contained in a single envelope.
Leftmost is the Burroughs Trochotron beam switching tube (~1950), using an electron beam which can take any of 10 stable positions. Beam control is partly magnetic: the second object is a similar tube surrounded by its cylindrical magnet (which is normally fixed to the glass tube). Trochotrons seem to have been used in Univac computers too. The third tube is a Philips E1T (1968), also using a beam switcher, in this case controlled electrostatically. The beam position can be read from a window, making a separate indicator superfluous. The tubes were mainly used in fast counters, for instance in particle physics.
Rightmost is a Dekatron tube (this one made by Mullard), using a gas discharge principle much like the Eckert-Mauchly counter. Here the status of the counter can be viewed through the top side of the tube. Dekatrons were used for slower counters, or in clocks, but also in the recently (2012) restored British Harwell computer (1951).
The ring counter was donated by the 'Rijksbureau voor Kunsthistorische Documentatie', The Hague, The Netherlands. Its origin is unknown; as far as we know a machine of this type has never been used in The Netherlands. At least it is not a part of a minicomputer of the 1970's as supposed by the previous owner...
The various counter tubes (lower picture) are in a private collection.
