ICL 2903 mainframe keyboard

Illustrated below is the keyboard from an ICL 2903 mainframe computer. The keyboard unit is a Micro Switch SW Series assembly with catalogue listing 84SW11-4, written “84 SW 11-4”. The PCB is marked “FREEPORT, ILLINOIS U.S.A.” while the product label gives “DÖRNIGHEIM W. GERMANY”. This is possibly only the second Micro Switch keyboard discovered that was assembled at Honeywell’s plant in Dörnigsheim, West Germany.

Three switch types were used: 1SW13 alternate action for the Shift Lock key, 1SW51 for the modifier keys and 1SW17 for the remaining keys. 1SW17 is believed to be sink pulse, making this an N-key rollover model. The two shift keys are stabilised using switch-like assemblies and half-force springs.

The PCB part number is SW-11328 and the encoder is model SW-20275 manufactured by National Semiconductor. Output is believed to be 6-bit ASCII, but this is not yet confirmed.

The production date is 74/50 and the serial number is 000339. The owner reports that “multiple sources state that ICL sold close to 3000 of the 2903/2904/2905”.

The photographs were provided by the owner, “Blazemage2001”, and are placed into the public domain.