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Singer/Friden EC1117A Desktop Calculator

Updated 10/24/00

This particular calculator is interesting because it is a revision of a physically and functionally identical earlier machine, the EC1117. The earlier EC1117 uses Nixie tube displays rather than the individual vacuum fluorescent display tubes used in the 1117A. One can surmise that this 'update' was done to reduce the cost of the machine, using less-expensive VF tubes in place of more complex and costly Nixies. Whether the reduction in manufacturing cost was passed along to the consumer is a question which remains unanswered. The mechanical hardware (case, keyboard assembly, etc.) are identical between the 1117 and the 1117A. Electronically, the differences are related to differences in driving Nixie tubes versus the segmented VF display tubes.

The 1117A uses a multi-chip set for its calculating brains, placing it between the early IC calculators which used small-scale integrated circuits (such as the Brother Calther 412), and slightly later IC machines which have all of the brains on a single chip (like the Canon L100S). Based on date codes on some of the components, the machine was built in the early 1972 timeframe. The machine has a Singer badge on it, with 'Friden EC1117' (note the missing 'A' designation here) silkscreened onto the keyboard bezel as the model number. In 1963, Friden was purchased by Singer, and became the Friden Division of Singer, which explains the seemingly contradictory badging on the machine. As part of Singer's takeover of Friden, it was decided that it wasn't cost-effective to continue making the calculators domestically, so Singer partnered with electronics manufacturer Hitachi in Japan to design and fabricate the electronics in these machines. Hitachi sold a functional equivalent to the 1117A in Europe as the Hitachi KK521. The KK521 is very similar cosmetically to the EC1117A, with subtle differences in keyboard nomenclature, cabinetry, and materials, as well as minor differences in main circuit board layout, but functionally, the machines are for all intents and purposes, identical.

Friden 1117A Insides

The machine uses a 3-chip IC set made by Hitachi (HD3234, HD3235, and HD3236) for the main calculating engine, with a number of small Hitachi SSI (Small-Scale Integration) chips serving glue functions, and a couple of oddly packaged parts situated near the display tubes which appear to be early display driver IC's. These display driver "chips" are identical in packaging to those found in the slightly later-produced Canon L100S, though the part numbers on them are different, probably because the L100S uses a Panaplex-style display while this machine uses vacuum fluorescent tubes. The individual display tubes use an unusual 8-segment digit design. The circuit board for both the keyboard and main circuit boards have Hitachi logos on them, which indicate that Singer farmed out the design and manufacture of the circuitry for the machine to Hitachi. The fact that the display frame has 'spaces' for an additional four display tubes indicates that at at least the display frame was a 'generic' part which could be used in other machines. Even though Singer owned Friden and mandated that the circuitry be built off-shore by Hitachi (for cost-cutting reasons), the Friden influence can still be seen in the machine, with a very beefy all-metal upper-case; a massive metal carrying handle which folds into the bottom of the case; and the Friden trademark brushed metal band encircling the keyboard area.

Closer View of Main Circuit Board

The 1117A is a pretty standard four-function desk calculator, with 12-digit display. It has a single memory register, with M+ and M- keys to add or subtract the content of the display to/from the memory register. It also has two different memory recall keys, one which leaves the memory register intact, and the other which recalls the memory register to the display, and clears the memory register. There are three annunciators at the right side of the display which indicate Overflow/Invalid operation (strangely labelled UDF, which also seems to double as a 'busy' indicator); negative sign; and an indicator which lights when the memory register has non-zero content. There are two rotary knobs to the left of the keyboard. The upper knob controls memory summing and constant multiply/divide functions, and the lower one selects the number of digits behind the decimal point for results in the display. A small slide-switch turns rounding mode on or off. The machine isn't a speed demon, with the ubiquitous 'longest' division of all nines divided by one taking approximately 1 second to perform. The display blanks during calculation and the 'UDF' annunciator lights while operations are occurring.

Detailed View of Keyboard Construction

The keyboard of the machine uses high-quality keycaps with molded in nomenclature. The key stalk has a small magnet attached to the end of it which actuates glass-encapsulated magnetic switches to close the circuit for each keyswitch. The keyboard connects to the main circuit board via an edge connector. The machine uses a standard linear power supply, with an odd three-prong mains cable which has "Friden" molded into it -- the same type of power cable used on the old Friden electro-mechanical calculators.

Text and images Copyright ©1997-2021, Rick Bensene.