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Casio 121K

Casio 121K

Casio 121K

Distinctive features: Large desktop calculator using electronics transitional between Medium-Scale Integration (MSI) and Large-Scale Integration (LSI).

Capabilities: 4-functions.

Display: 12 digits "Nixie"-type tubes.

Technology: Fairchild LSI (Large-Scale Integration) integrated circuits SL-35021, SL-35022, SL-35023, SL-35024, date coded to the beginning of 1971, & 21 MSI (Medium-Scale Integration) integrated circuits on 2 boards 250x140mm (10x5").

250 mm wide, 290 mm deep, 80 mm high (10" x 11.5" x 3.5"), 2 1/2 Kg (5.5 lbs.).

Made in Japan.

Has similar electronics to the Casio AS-C but a completely different looking calculator.

Inside Casio 121K

With the cover removed.  On the right is the upper circuit board, the lower circuit board is folded underneath.

Casio 121K circuit boards

The two circuit boards removed and unfolded.  The four Fairchild LSI chips are on the left circuit board, which was the lower board.

Casio have always been at the forefront of the development of electronic calculators.
Fairchild, one of the giants of the semiconductor world at this time, were only briefly involved with calculator integrated circuits.

The 4 large ICs among a scattering of small ones illustrates the growing takeover of the electronic functions by Large Scale Integrated-Circuits (LSI) at this time.

Vintage Calculators

© Text & photographs copyright Nigel Tout   2000-2021  except where noted otherwise.