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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).
Internal view. |
Main logic board with registers and state machine. |
Timing and display board. |
1G51400 | |
1971 (PCB edge connector labeled 71.5.07) | |
2020 Mar 27 | |
ebay Calgary | |
Good physical condition. Small piece cracked at rear of top half of case. '6' key is very bouncy. | |
Functional (2020 Mar). |
2020 Mar | |
Bouncy '6' key. | |
Bottom guidepiece of the keyswitch had fallen out, along with two small rubber bumpers that fit on the sliding tab. Bumpers set in place and guidepiece snapped back in. Guidepiece should be glued, may pop out again with too much force on key. |
2020 Mar | |
Broken piece of case top glued back in (CA). Also, crack found at right front of case, glued. |
TEAL Royal Digital I
Calculators | Integrated Circuits | Displays | Simulations EEC |
bhilpert |