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Singer/Friden EC1114 Calculator

This exhibit is made possible through the gracious donation of a working Friden EC-1114 by Linda Miller of Maryland Specialty Wire, Inc. The EC-1114 was used in the business for many years, before suffering a failure, and put aside. Fortunately, Linda found the Old Calculator Web Museum, and made the machine available for donation. Once the machine was recieved, it was found that the problem was easily fixed by simply cleaning the various connectors in the machine, and it now works like new. Sincere thanks to Linda for making this exhibit possible.

Updated 12/19/2010

The Singer/Friden EC1114 is a good example of an early small & medium-scale integration MOS 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 from the mid-1970 timeframe, 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. Hitachi marketed this calculator in their home market (Asia) as the Hitachi ELCA-24.

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 second 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.

Text and images Copyright ©1997-2011, Rick Bensene.