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Singer/Friden EC1116 Desktop Calculator

Updated 12/11/2005

The Singer/Friden EC-1116 is, feature-wise, top of the line calculator in the 111x-line of machines designed and built by Hitachi for Singer/Friden. The 111x-line of machines include the EC-1112, a first-generation all-transistor machine that began the line. Later, the second generation EC-1113 hit the market utilizing Hitachi's first-generation MOS (Metal Oxide Semiconductor) small-scale integrated circuits. Shortly thereafter, improvements in MOS technology allowed somewhat higher levels of integration, through the use of the HD-3100-series of MOS IC's, especially designed by Hitachi for electronic calculator applications, used in the third generation 111x-series calculators, which included the EC-1114, EC-1115, and lastly, the EC-1116. Of the two, the 1116 most closely resembles the EC-1114, with a very similar keyboard layout, and virtually identical cabinet and internal structure. The fourth generation in the 111x-series included the first of early large-scale MOS integrated circuits. These machines, which included the EC-1117 and EC-1118, dramatically decreased the number of integrated circuits necessary for a fully-featured calculator. Lastly even higher levels of integration in the EC-1117A made up the last of the series. The 1116 topped all of the machines in the series in terms of features, with two full-function memory registers, one-key square root, automatic accumulation modes, constant for multiplication and division, round-off mode, and a full sixteen digits of capacity. The price for such functionality was fairly high, with the 1116 selling for $1,195 in early '71, which was probably somewhat discounted from its initial introduction price. It appears that the 1116 was introduced sometime in the early part of 1970, and was actively marketed through mid-1973.

Front Cover of the Operating Instructions for the 1116

The 1116, like all of the other Singer/Friden 111x-series calculators, was designed and manufactured by Japanese industrial giant, Hitachi Ltd. Hitachi badged the machines with Singer/Friden logos and color schemes for distribution by Singer/Friden, through an OEM agreement. Hitachi sold similar calculators with their own branding in Europe, but because of the OEM agreement with Singer/Friden in the US, the Hitachi-branded calculators were not marketed in North America.

Closeup View of IC's Used in the Friden 1116 (Note Hitachi Logo Upper Right)

The 1116 uses the same general design as the less-capable EC-1114 and EC-1115, utilizing Hitachi-made second-generation HD-31xx-series small and medium-scale PMOS integrated circuits, packaged in ceramic dual-inline packages. A total of 78 IC's and 46 transistors make up the logic of the machine, with most of the IC's containing of a few logic gates or flip-flops. A sprinkling of medium-scale devices are also used in the machine. A number of Hitachi HD3109 shift register chips (each containing a 60-bit shift register and two four-bit shift registers) combine to form the working and memory registers of the machine. An HD3112 bit-serial BCD adder also takes advantage of higher-levels of integration to form the foundation of the machines arithmetic logic unit. The 1116, along with the 1114 and 1115, are somewhat unique for their time in that they utilize a completely solid-state design. Calculators from other manufacturers of the time, such as Canon, Sony, Wang, and Casio, used magnetostrictive acoustic delay lines or magnetic core memory for calculator data storage elements, both of which were complex and expensive. Hitachi's use of integrated circuit devices for register storage began the trend towards elimination of these somewhat exotic data storage methods in favor of higher-levels of integrated circuit technology.

Friden 1116 Internal View

Functionally, the 1116 is quite capable for its time, as far as a business desktop calculator in its price range goes. The calculator provides a full sixteen digits of capacity, with fixed decimal point settings from zero through twelve digits behind the decimal point, making the machine useful for just about any application from banking to engineering. Two accumulating memory registers with automatic summation modes make the calculator especially useful for business and statistical calculations. The machine's automatic one-key square root function is useful for engineering, statistical, and general mathematics.

The 1116 is quite easy to operate, with familiar keyboard controls, and a generously-sized keyboard with keys that operate smoothly and quietly. The keyboard uses magnetically actuated reed switches, making the keyboard very reliable. The keyboard bezel is a beefy cast-metal structure, with a painted panel and chrome accents. The keycaps are made of a hard plastic, with moulded-in nomenclature to prevent the keycap legends from wearing off. A smoked plastic cover fits over the keyboard and display area to serve as a dust cover.

The keyboard is grouped into three sections. The left-most section contains the clearing-related functions, with the [T1] and [T2] keys recalling memory register 1 and 2 to the display, then clearing the memory register. The [CE] key clears the input register, allowing incorrect entries to be cleared without affecting any math operation in progress. The larger [C] key clears the calculator working registers, but leaves the memory registers intact. The center group of keys makes up the standard numeric keypad. The right-most group of keys provide controls for the math operations of the machine. The usual [+=] and [-=] keys provide for adding machine-like addition and subtraction. The [X] and [÷] keys operate as expected, entering the first number of a multiplication or division operation, and preparing the machine for entry of the second number. Pressing the [+=] key finishes off a multiplication or division operation, calculating and displaying the result. The calculator is capable of chain operations, allowing an operation such as "3 X 5 X 7" to be performed by simply pressing [3], followed by [X], followed by [5], followed by [X], followed by [7], then pressing the [+=] key to display the final result of 105.

Detailed View of Friden EC-1116 Keyboard Controls

The [R] key swaps the content of the two working registers of the calculator. This is useful for performing reciprocal division. For example, entering [3], [÷], [1], [R], [+=] will provide the result of "00000000000000.33" with the decimal point selection at 2. The [Square Root] key calculates the square root of the number currently in the display. The [M1+] and [M1-] keys add or subtract the content of the display to/from memory register 1. Likewise, [M2+] and [M2-] perform the same operations on memory register 2. The [S1] and [S2] keys recall the content of memory register 1 or 2 to the display, leaving the memory register intact. The push-on/push-off [K] key activates the constant function, retaining the first number in multiplication and division problems for repeated use. Another push-on/push off key with a summation symbol enables automatic accumulation of products or quotients in memory register 1.

A large rotary knob located in the lower left corner of the keyboard panel is used to set the fixed decimal point location, anywhere from zero to twelve digits behind the decimal point. The 1116 is a fixed decimal output, floating decimal input machine. It is possible for the user to enter numbers with more than the number of digits behind the decimal point indicated by the decimal point selection knob. The calculator will discard or round off any entra digits, depending on the setting of the "R/O" (Round Off) slide switch, which is located above the numeric keypad. Another slide switch, with two positions labeled "OFF" and "ΣMD" controls the accumulation of multiplicands and dividends in memory register number 2. A push-on/push off switch with a bright red button controls the power to the 1116. At the upper right corner of the keyboard is a slider that positions a series of orange pointers which group the numbers on the display in groups of three for easier reading of large numbers.

Two indicators labeled "M1" and "M2" at the right end of the display indicate when the corresponding memory register has non-zero content. Another indiciator in this area lights to show that the number in the display is negative. At the left end of the display, two more indicators provide status of the machine with regard to overflow conditions. One indicator, labeled "UDF" lights to indicate that the calculation just completed resulted in an answer that has more than 16 significant digits. In this case, the result in the display is accurate to sixteen places, but any additional digits are lost. The manual calls this indication an underflow condition, which seems rather counter-intuitive, as such a condition is usually called an overflow. A second indicator, labeled "DS", for "Decimal Shift", lights to indicate that the whole number portion of the displayed result is larger than 16 minus the value set on the decimal point position selector. Why the designers opted for such a complex overflow indication scheme is a mystery.

The Circuit Boards of the 1116

Internally, the 1116 is built on virtually the same chassis as the 1113 and 1114 calculators. The moulded plastic cabinetry parts are interchangeable between the three machines, and the internal chassis is very similar. The 1116 uses a total of four plug-in circuit boards for its logic. A fifth circuit board provides power supply regulation. The logic boards plug into a hand-wired backplane that provides the interconnections between the boards. The circuit boards are made from bakelite, and have copper traces on both sides of the board, with soldered, plated through holes providing connections between each side of the circuit board. The edge connector fingers on the circuit boards are gold-plated for reliability. The logic boards have a metal edge crimped along three sides to act as a stiffener, and serve as guides for sliding the circuit boards into the chassis. The chassis is made of stamped sheet metal. The chassis is not overbuilt, such as those in competitor Sony's calculators, but it is sufficient to handle the rigors of shipping and office handling with no problems.

Smoked Plastic Dust Cover

The 1116 has a few quirks, along with the already strange overflow notification methods. The machine does not provide any error indication for illegal operations, such as extracting the sqaure root of a negative number, or division by zero. Performing the square root of a negative number simply returns a result as if the throws the machine for a real loop (literally), with the machine beginning a counting sequence, racking up approximately 485 counts per second. Pressing the [CE] key during the counting will reset the count to zero, but as soon as the key is released, the counting resumes from zero. The calculator is unresponsive to all other keys on the keyboard, except the [C] key, which ends the chaos, restoring the machine to normal operation.

The 1116 has an odd connector located under the keyboard assembly which isn't present on the 1114 or 1115. Up until recently, the purpose of this connector wasn't known. As it turns out, The connector is for an add-on peripheral device called an item counter. The item-counter is a side-car device that attaches to the right hand side of the calculator, that has a small pigtail connector that plugs into the connector under the keyboard of the 1116. The item counter has a three digit electro-mechanical counter that advances upon the depression of the [+=] or [-=] keys on the keyboard. A manual pushbutton on the item counter clears the three digit counter to 0 when depressed. A small access hole exists in the cabinetry of the 1116 to allow the pigtail wire access to the inside of the 1116. This device is useful in helping perform average, standard deviation, and other statistical functions with the 1116 calculator. It is not known at this time what this option cost. It was designed to be field installed by a Singer/Friden service technician.

The 1116 performs at about average speed for machines of this era. Complex square root operations can take up to 1.25 seconds to complete, with the Nixie tubes madly flickering during the process. Dividing 9999999999999999 by 1 (with decimal point location set at 0) takes just about 1 second. Multiplication of 99999999 by itself takes about 3/4 second. The "UDF" indicator doubles as a "busy" indication, and lights during the time the calculator is busy generating the result. Addition and subtraction, both in the working registers and to the memory registers, is nearly instantaneous, with only a quick flicker of the Nixies and UDF indicator showing the operation occurring.

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