Friden 1112/Hitachi ELCA 12 Technology
Friden 1112 Calculator Internals, LHS
The Friden 1112, or more correctly the Hitachi ELCA-12, looks and feels very much like a first attempt, which indeed it was.
Architecture
The architecture is counter-based, like mechanical calculators of the mid-20th century. This can be seen from the internal layout where each display digit is on its own PCB, the board having an obvious 4-bit counter which is directly decoded and displayed. This is similar to the counter wheels of mechanical calculators. Electronic logic to run the counters in addition or subtraction takes the place of mechanical linkages. Further logic manages the shift-and-count of multiplication or the serial subtractions of division. It’s cute to watch division dance across the nixies, since there is no display suppression during operations.
Electronics
The electronic implementation is old-fashioned for 1967, using 2SA17 germanium PNP tranistors for almost all of the logic. Silicon had superseded germanium in US machines by the mid 1960s, due to the electrical fragility of germanium devices and their sensitivity to temperatures in the high-domestic range.
Friden 1112 Calculator Keyboard with leaf switches
Construction
Hitachi’s PCB layout and fabrication is basic, the boards are single-sided with wide traces laid out in an expansive manner. This makes all the boards larger than they need be and denied Hitachi the opportunity to make a very much smaller machine. It’s interesting here to compare the size and capability of the IME machines of the same era.
The mechanical design is better than some early Japanese machines. Awkward insertion/removal of PCBs is the main irritation when servicing, and the vertical rear backplan connectors prevent the use of typical straight extenders.
The keyboard is a custom-engineered arrangement of leaf switches, mechanically complicated, requiring acccurate adjustment for reliability and robust debouncing electronics. The use of such a basic approach suggests that the designers were not aware of options such as reed switches or mechanical microswitches.
None of the above is intended as a criticism of the Japanese engineers of the mid 1960s. Rather, it seeks to describe a jumping-off point for the Japanese electronics industry, after which it made most impressive progress in a very short time