| +Home | Museum | Wanted | Specs | Previous | Next |
Singer/Friden EC1114 Calculator
Updated 10/19/2005
The Singer/Friden EC1114 is a good example of an early small & medium-scale integration IC-based calculator. The machine is a rather basic 14-digit four-function calculator with memory, typical of desktop office calculators of its time. The machine has IC's with date codes ranging from mid-1970, so I would target this machine as being built sometime in mid to late 1970. Once Singer bought out Friden, most all of the calculator design and manufacturing was farmed out to the Japanese electronics giant Hitachi. The 1114 was entirely designed and manufactured for Singer/Friden by Hitachi.
The Singer/Friden EC1114 Minus Top Cover
The 1114 is built from five circuit boards
that plug into a backplane with hand-wired interconnects. The boards stack
vertically inside the machine, arranged in a sheetmetal cage which provides
a frame for securing the circuit cards. Rubber isolation blocks provide
some shock mounting for the boards. The circuit boards have a metal edging
crimped around their perimeter to act as a structural enhancer to minimize
flexing of the circuit boards due to the fact that there is no support for
the circuit boards except along the edges.
Internals with Keyboard Assembly Removed The top circuit board in the stack is smaller than the other boards,
and provides keyboard encoding functions, along with power supply
regulation and filtering. The 2nd board contains the display subsystem,
including the 14 Hitachi CD 79 Nixie tubes and their associated driving
circuitry, which is made of mostly discrete components. The remaining
boards comprise the calculating logic of the machine, and are populated
with numerous small-scale and medium-scale integration IC's, with a lot
of diodes, resistors, and a few transistors sprinkled amongst the chips. The Circuit Boards of the EC1114 All of the 59 integrated circuits that make up the logic of the 1114
are Hitachi-made HD31xx-series PMOS devices. The HD31xx-series devices
consist of small and medium-scale circuits, containing at least a couple
of gates or flip-flops, or at most a multi-bit shift-register or binary coded decimal serial adder.
The date code used on these Hitachi parts are different than used on
US-made integrated circuits.
The code consists of a single digit, which is the last digit of the
year of manufacture, followed by a single letter (A-Z), which appears to
indicate a two-week period in the year (A=week 1/2, B=week 3/4 ...
Z=week 51/52) in which the part was made. This is in contrast to the now
more standard date codes which are indicated by YYWW, with YY being the
last two digits of the year, and WW being the week in the year in which
the part was manufactured. Keyboard Detail The EC1114 is a very conventional machine for its day. It operates
in (per the operators manual) "floating decimal input, and fixed decimal
output". This means that on input, the decimal point can be positioned
anywhere, but displayed results will always have the decimal point at
a fixed position, which is determined by a rotary switch on the keyboard panel.
The decimal point can be set at any position from 0 digits 9 digits behind the
decimal point. The memory operates conventionally, with [M+] and [M-] keys
for adding or subtracting the display to/from the memory register,
memory recall ([S]), and memory recall/clear keys ([T]). A push-on/push-off
'sigma' key allows for the sum of products or quotients to automatically
accumulate in the memory register. The machine provides a [K] constant
key which is a push-on/push-off key that enables the constant function
when depressed. The constant mode works for multiplication and division only.
The [R] key swaps the content of the hidden 'operand' register and the
display. The [CE] key clears the display of erroneous entries, and the [C]
key clears the entire machine except for the memory register. A small
slide switch sets the rounding mode of the machine.
Hand-Wired Backplane Indicators on the left end of the display indicate Error/Overflow
(labeled UDF, which, according to the manual, stands for UnDerFlow, which
seems a misnomer to me), and another, labeled "M", which indicates
when the memory register conains a non-zero value. A similar annunciator
on the right end of the display indicates a negative number in the display.
Cover of the EC1114 Operator's Manual The EC-1114 is measurably faster than its predecessor, the
Friden EC-1113.
Addition and subtraction complete
virtually instantly. Multiplication and division involve slightly more
time to complete, but no calculation, even the museum's "all 9's divided
by 1" calculation takes more than perhaps 1/5th of a second to perform.
The displays are left active during calculation, and in more complex multiplication and division problems, the digits dance through the display in a hasty
blur before the result is displayed.
