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Sanyo ICC-1141 Electronic Calculator

Updated 6/17/2010

This machine turned out to be a bit of a surprise. I found a party that had the machine for sale a while back, and when I first looked at the photos of the machine and read the description the owner provided, I thought, "It looks too new, but it also looks rather large for a 1980's calculator". I almost passed it off as being too new a machine for the museum. In retrospect, I'm quite glad I didn't, because as when it arrived, it was in absolutely beautiful condition, and when I opened it up, I was stunned to find that it was an early MOS IC-based calculator from the 1968 timeframe! This machine is an example of Sanyo's second-generation of electronic calculators, with the earlier ICC-121, ICC-141, and ICC-162 calculators making up the first-generation. These earlier machines used similar MOS IC technology, but were built in a more modular fashion, and used incandescent lamp-lit seven segment display technology.

Profile view of Sanyo ICC-1141

Sanyo, a multi-national company based in Osaka, Japan, has been in business providing a wide range of products and services since the late 1940's. Included in the mix are consumer electronics, appliances, power systems, transportation and logistics, and much more.

This ICC-1141 appears to have been manufactured in the mid-1968 timeframe (based on somewhat cryptic date codes on some of the integrated circuits), and uses early Japanese-design MOS IC technology. The construction of the machine is quite unique, leading me to believe that the design and manufacture of the calculator was done solely by Sanyo, rather than 'farmed out' to companies like Hitachi or Casio, who would provide design and manufacturing services for other calculator marketers.

Sanyo ICC-1141 Circuitry

The IC's used in the machine contain from between a few logic gates or flip-flops, to higher-level integration functions such as multi-bit shift-registers. Compared to earlier all-transistor technology, these early IC's made it possible to shrink down the size of a calculator while providing the same functionality as the larger all-transistor machines. Most of the logic of the ICC-1141 is implemented using IC devices, but there is still a bit in the way of discrete diode/resistor gates and transistor-based logic in the machine. At the time the machine was made, a careful balance had to be struck between the cost of new technology like integrated circuits, versus the extra space and power required by discrete technology. As integrated circuit technology advanced, the cost of IC's came down, and by later in the 1960's, it was possible to build a calculator with a minimum of discrete component logic, with the discrete devices relegated to functions such as power supply regulation and display drivers. By 1970, Large Scale Integration (LSI) IC devices appeared on the scene, and the whole world of calculator technology completely changed... what used to take from between 70 to 150 small-scale IC's could be crammed into four large-scale devices. The age of the large, heavy, A/C-power-hungry desktop calculator was nearing its end.

The Sanyo ICC-1141 Model/Serial Tag

The 1141 is a very well-built machine. The logic of the machine is contained on two large circuit boards stacked atop each other, that take up the majority of the real-estate across the bottom of the machine. The boards plug into dual edge-connectors with a hand-wired backplane to provide connections between them. The boards are secured within the cabinet by a fairly complex plastic casting that provides spacing between the boards, as well as stiffening for the unusually large circuit boards. The IC's are a mix of can-packaged IC's, and DIP (Dual-Inline Package) devices with ceramic cases. Most of the IC's are made by NEC (uPD01x in can packages and uPD1xx in DIP packaging), but a few Mitsubishi IC's are also sprinkled about in the circuitry. The pheonolic circuit boards have etch on both sides, with an unusual number of jumper wires to provide connections on the component side of the board that couldn't be made via etched connections because of real-estate limits. Feed-thrus are soldered through with small wires placed through the holes to assure reliable side-to-side connectivity.

The Early Seven-Segment, Gas Discharge Display used in the Sanyo ICC-1141

The 1141 uses fourteen wonderful seven-segment gas-discharge display tubes for its display. The display board connects to the main electronics via two edge connectors and cables. The display on this machine is very unusual for the time. Many machines of the late 1960's used Nixie tubes for display, because the decoding and driver circuitry was quite simple... most of the calculators of the time represented numbers internally in BCD (Binary-Coded Decimal) form, and only a simple BCD to "1 of 10" decoder feeding a driver transistor was needed to drive a Nixie tube. Seven segment displays are somewhat more complex, as each BCD code needs to be converted into a pattern of bits that drives the individual segments appropriately. Until IC's became avaialable to do the 7-segment decoding, Nixie tubes were the 'easier' display technology to implement. However, Nixie tubes were rather difficult to manufacture, thus making them somewhat expensive, and as other easier to manufacture display technologies became available (such as vacuum-fluorescent and Burroughs Panaplex seven segment display devices), Nixie tubes eventually fell from favor. Even though Nixies may have been easier to use, apparently Sanyo found some advantage to the seven-segment type of display, and implemented the display of the 1141 with this technology.

The gas-discharge seven-segment display tubes work in a similar fashion to a Nixie tube, but rather than having ten individual electrodes shaped as digits, seven electrodes are arranged in a segmented '8' pattern, allowing combinations of the segments to be lit to form any digit from zero through nine. The tubes are filled with a similar gas to that used in Nixie tubes, that, when an appropriate voltage was delivered to a segment electrode, will cause the segment to glow. Lighting the appropriate pattern of segments forms any digit from zero through nine. Each tube also contains an electrode for a decimal point, situated below and ever so slightly to the right of each digit.

Two incandescent indicators are situated at the left end of the display panel, one lights to indicate a negative number (when all digit positions are occupied), and the other lights when an overflow condition exists. An unusual feature of the machine is an audible alert that sounds when an overflow condition occurs. In an office environment, this seems like it would be an extremely annoying feature. Three incandescent indicators are used to display the status of the machine. These indicators are located on the keyboard panel, behind red jeweled panels. One indicator, labeled "M", lights up when the memory register has non-zero content. The other two indicators light up after the first operand of multiply or divide calculations have been entered, to remind the user of the operation in progress. An "X"-labeled indicator lights after the [X] key has been pressed, and a ÷ symbol denotes the indicator that lights after the [÷] key has been pressed. After the operation is completed, the indicator for the funcion is extinguished. Some early Sharp electronic calculators provided a similar function, but integrated the lamps into the key assembly such that the X or ÷ symbol in the keycap would glow when the operation was pending.

Along with using an unusual (for the time) display technology, the 1141 also provided a number of other functions that were ahead of its time. The display system provides leading-zero suppression, which was quite uncommon at the time. Leading-zero suppression really only became a common feature once large scale IC technology was available -- a feature that was relatively easy to squeeze into a calculator chipset, but required some additional (and cost-increasing) circuitry in less-highly integrated calculators. The blanking of leading zeroes makes reading numbers in the display easier, as the eye isn't distracted by all the extra zeros. Another unusual feature is that, if the number on the display is negative, the "-" is displayed using the digit display tubes rather than with a separate indicator, as was very common on calculators of this vintage. The machine also provides an automatic summation mode, activated by a push-on/push-off key on the keyboard (with a 'sigma' nomenclature) that automatically accumulates the results of multiplication and division operations into the memory register. The 1141 has a single memory register that operates as an accumulator, with [M+] and [M-] keys adding or subtracting the number in the display from the memory register, and placing the result back into the memory register. The [CM] key clears the memory register, and the [RM] key recalls the content of the memory register to the display. The Sanyo ICC-1141 also has a constant function, activated by a push-on/push-off key labeled [K]. When the constant function is turned on, a constant multiplier or divisor is retained, and can be used for repeated operations with differing multiplicands or dividends, or the constant can be repeatedly applied for use in power sequences.

The Keyboard Assembly of the Sanyo ICC-1141

The keyboard panel of the machine is populated with the expected operator keys, with a few minor deviations from the norm. The keyboard uses magnetic reed switches, making for extremely smooth and reliable operation. The Clear Entry function, usually [CE] on many calculators, is [CK] on the 1141, for "Clear Keyboard". This key clears any number that has been entered thus far, allowing for correction of input errors. The [CA] key (for Clear All) does the obvious, clearing the machine (with exception of the memory register), making it ready for calculations. The [RC] key swaps operands on multiplication and division operations. A series of five pushbuttons occupy the left-hand side of the keyboard panel. These buttons, labeled "0", "1", "2", "4", and "8", select the fixed decimal point location in the display. Pushing one of these keys will cause any previously selected key to be deselected, and the new key to be 'latched' down. A slide switch selects the rounding mode of the machine, with truncate, and 5/4 positions.

The ICC-1141 has a number of quirks which seem to be common on early small-scale integrated circuit calculator implementations. First off, any multiplication or division problems will give false overflow conditions if either operand contains 14 significant digits. For example, 99999999999999 X 1 will result in an overflow condition, even though it is within the fourteen digit range of the machine. Also, pressing keys on the keyboard while the machine is busy calculating will cause an overflow condition to occur most of the time. Sometimes, though, the result will be an incorrect answer, which is a somewhat serious bug in the machine's logic. The machine also gets somewhat confused about the value of zero, allowing the existence of -0. Performing 1 [-=] 1 [+=] will result in -0. An odd quirk that I've not noted in other calculators is that calculations using zero as the multiplicand causes the machine to go into a very strange state, that can only be cleared by power-cycling the machine. As with many other machines of the era, division by zero causes the machine to get confused, but in this case, pressing the [CA] key will return the machine to normal operation. During calculations, the 1141 lights all decimal points, and leaves the displays active, causing quite a light show on longer calculations. The machine is somewhat slow compared to other machines of similar vintage, with thirteen 9's divided by 1 (remember, the machine can't handle multiplication or division with 14-digit operands) takes a little over 3/4 second to perform.

Sanyo marketed another machine called the ICC-1121 that was identical in all aspects to the 1141 except (as expected) that it provided 12 digits of capacity versus the 14 digit capacity of the ICC-1141.


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