Early Electronic Calculator Desktop Calculator Photo Gallery

Sony SOBAX 2500 1970 Logic Technology: SSI Memory Technology: DELAY-MS Display: NIX This calculator is based on a small IC family proprietary to Sony. Unfortunately these ICs have a propensity to fail (see the notes about the ICs), making it difficult to keep these calculators functional. I received two units and was originally able to restore both of them to functionality, but one has since been relegated to being a sacrificial unit for ICs. Notable technically for the use of a magnetostrictive delay line in longitudinal mode, in contrast to the more usual torsion mode. Also, a channel slice in the delay-line is filled with a fixed pattern at power-up. The bitstream from this channel feeds a phase-comparator in a Phase-Locked-Loop arrangement with the master clock as VCO. The master clock is thus tweaked to keep it in sync with temperature variation of the delay-line latency.

TEAL IME 41 1970 Logic Technology: DIS,SSI,MSI Memory Technology: MSI-MOS Display: VFI OEM: TEAL Another basic four-function-with-accumulator OEM'd by TEAL, here for the Italian IME. The electronics & logic design of this model and the TEAL Riccar are essentially identical. The main differences between them are the display - vacuum-flourescent for the IME-41 versus Nixie for the Riccar, and the IME having additional features of 5/4 rounding and a double-zero key. The calcuseum site shows the apparently same OEM model badged as the Busicom 121-DB and as an NCR model.

Toshiba BC-1212 1970 Logic Technology: DIS,SSI,MSI Memory Technology: MSI-MOS Display: NIX At the user level this is a standard-for-the-period 4-function-with-accumulator model. Technically, it is notable for a nice, clean, canonical state-machine design, implementing straightforward multiply and divide algorithms. Compared to many of it's period, it's easier to understand at a detailed technical level. It's a good candidate for examination into how bit-serial machines of the era work. The reverse-engineered schematic includes a state diagram and state action descriptions.

Canon Canola EP151 1971 Logic Technology: SSI,MSI,LSI Memory Technology: MSI Display: PRI While the mechanical calculator market declined into oblivion around the early 1970s, there was still a demand for printing calculators. This is an early example of an electronic printing calculator. There is no display besides the printer and it doesn't print keypress digits until the entire number is entered. The printer uses a form of electrographic printing requiring special paper. Rotating styli scan across the paper delivering high-voltage pulses to burn pixels on the paper. A MOS character generator ROM like those used in CRT computer terminals of the day is used to generate the character pixel patterns. Variations of electrographic printing go back decades earlier, for example Western Union Desk-Fax facsimile machines from the 1940s.

Miida MC800 1971 Logic Technology: LSI-3 Memory Technology: LSI Display: VFI Regrettably, years ago I threw out the case and keyboard for my unit of this calculator, due to problems with the keyboard, but kept the electronics. Another calculator enthusiast (J.M.) was able to identify the model number and provided the photo of the complete unit.

Monroe 610 1971 Logic Technology: LSI-4 Memory Technology: LSI Display: NIX A nice space-agey-design NIXIE desktop. One of the last calculators to use a NIXIE display, and similarly a little unusual in combining a NIXIE display with LSI chips.

Monroe 650 1971 Logic Technology: LSI-7 Memory Technology: LSI Display: NIX The higher-end model of the Monroe 600 series.

TEAL Riccar 1971 Logic Technology: DIS,SSI,MSI Memory Technology: MSI-MOS Display: NIXIE OEM: TEAL A design from TEAL (Tokyo Electronic Application Laboratory), OEM'd for Riccar Sewing Machine Co. of Japan. Riccar doesn't seem to have given this calculator a model designation, this may have been the only foray by Riccar into calculators. From the design and implementation it appears to have very shortly preceded or be contemporary with the Royal Digital I, another OEM product from TEAL. This model features zero-blanking, unusual in Nixie and pre-microprocessor calculators, implemented at the expense of an additional IC and assorted components. The unit shown here is in the possession of Jef Ongena of Belgium. It had been in his family since new, but stopped working in 2020. Jef set out to repair it and found the power supply had failed. Repairing the power supply however, merely uncovered another problem. Repairing that uncovered a third problem, and so it went for six major faults, including four bad JMOS ICs. An over-voltage situation from the power-supply fault had likely taken out the ICs. After considerable effort, communication across two continents and a 'remote' reverse-engineering via photographs, Jef successfully restored the unit to full function. Replacements for two of the failed ICs were scavenged from orphan boards from an unrelated defunct calculator. This was fortunate as JMOS ICs are very difficult to obtain for repairs, but no such luck was forthcoming for the other two, which were of more complex functionality. In the alternative, substitutes were designed and constructed from 4000-series CMOS ICs. See the JMOS page for some commentary on this approach for repairing JMOS-based calculators, and the schematic for details.

TEAL Royal Digital I 1971 Logic Technology: DIS,SSI,MSI Memory Technology: MSI-MOS Display: VFI OEM: TEAL At a glance, based on it's size and vacuum-flourescent display tubes, this would appear to be an early LSI-based desktop from the early 1970s. The period would be correct - a 1971 date code was found inside. It's quite a bit smaller than the discrete and SSI-based calculators of the late-60s, so an LSI-based implementation would be expected, as by 1971 the transition to LSI was underway and a few LSI chipsets for calculators were available. Opening it up led to a surprise though. It's built from the JMOS series of SSI/MSI ICs, along with lots of discrete components. Rather than being amongst the first of a class, this is one of the last, likely the last basic 4-operation calculator model based on this low level of integration. The designers managed to get the IC count down to just 29. That's not a bad display tube in the right-most digit, it's an intentional half-height zero, produced by some special logic around the outputs of the 7-segment decoder. Royal is actually Royal Typewriter Company, a then long-established typewriter manufacturer. This calculator model is fairly obviously of Japanese manufacture however. The calcuseum site shows the apparently same model badged as the Litton Feiler RC120, and indicating it was OEM'd by TEAL (Tokyo Electronic Application Laboratory).

TEAL abc-800 1971 Logic Technology: DIS,SSI,MSI Memory Technology: MSI-MOS Display: NIXIE This model is an OEM product from TEAL (Tokyo Electronic Application Laboratory). The abc-800 and TEAL-designed Riccar share the same case, differing in the presence of an accumulating memory function in the Riccar. The abc-800 and the TEAL-designed Royal Digital I share a nearly identical logic design, differing in the display type and number of digits (abc-800:nixie/12, RDI:flourescent/10). Presumably the abc-800 was slightly earlier and the design adapted to produce the Royal Digital I. (Possession of J.Ongena.)

Victor 18-3441 1971 Logic Technology: LSI-7 Memory Technology: LSI Display: PRI I suspect the LSI chip-set utilised in this calculator is an example of Rockwell's first version of the PPS4 processor series. This speculation is based on some correlations with ICs from the later PPS4/2 version.

Miida MC1214 1972 Logic Technology: LSI-2 Memory Technology: LSI Display: VFM A sibling to the Miida MC840, in the same sleek wedge-shape case. The MC1214 is 12 digits rather than 8, and includes a user memory feature. The chipset here is just 2 ICs, in contrast to the 3 ICs of the MC840.