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Singer/Friden EC1117A Desktop Calculator
Updated 12/15/21
This particular calculator is interesting because it is a revision of a physically and functionally identical earlier machine, the Friden 1117. The earlier 1117 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 calculator, using less-expensive VF tubes in place of more complex and costly Nixies, as well as updating the technology used to implement it. 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 Hitachi KK-521
The 1117A uses a multi-chip set for its calculating logic, placing it between the early small/medium-scale IC calculators (such as the Brother Calther 412), and later calculators that have all of the brains on a single chip (like the Canon L100S). Based on date codes on some of the components, the exhibited calculator was manufactured in the early 1972 timeframe. The machine has a Singer badge on it, with "Friden EC1117" (note the missing "A" designation here) silk-screened 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 Singer badging on the machine. As part of Singer's takeover of Friden, it was decided that it was no longer cost-effective to continue designing and manufacturing calculators in the US, Singer partnered with electronics manufacturer Hitachi in Japan to design and fabricate the electronics for the 111x-series of calculators. Hitachi sold a functional equivalent of the 1117A elsewhere in the world 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 identical.
Inside the Friden 1117A
The 1117A machine uses a 3-chip IC set
made by Hitachi (HD3234, HD3235, and HD3236) for the main calculating engine,
with a number of additional Hitachi chips serving
glue functions, and a couple of oddly packaged parts that appear to be
hybrid circuit modules situated near the display tubes that appear to be
related to driving the vacuum-fluorescent display tubes. These display
driver devices 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 gas-discharge 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 empty spaces for four additional display
tubes indicates that at at least the display frame was a generic part that
could be used in other machines. The cabinet is the same as that used
for the earlier Nixie-tube display 1117, with
a very beefy all-metal upper-case; a massive metal carrying
handle that 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 basic
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 that leaves the memory register intact, and the other that 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
slide-switch turns rounding mode on or off. The machine isn't a speed demon,
with the ubiquitous most complex 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 key-caps 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 key-switch. 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.
