Singer/Friden EC1118 Desktop Calculator

The Singer/Friden 1118, along with the other machines in Singer/Friden 111x line of desktop electronic calculators, was purposefully designed to fit a specific niche in the office machine marketplace. The 1118 is one of the more feature-laden machines in the line of 111x machines, but the feature-set is definitely targeted at a more complex business customer. With a base price of $595 back in 1971, buyers of this machine would likely think carefully about casually plunking that kind of money down for a machine with more functions than needed. But, for those that needed the flexibility of the 1118's dual accumulating memories, automatic summation functions, and high capacity, the 1118 was just the ticket.

A Close-up View of Early Hitachi LSI IC's used in the 1118

The 1118, like all of the other Singer/Friden 111x-series calculators, was designed and manufactured by Hitachi in Japan. Hitachi built the machines for Singer/Friden and the calculators were distributed and services by Singer/Friden in their markets. Hitachi marketed essentially an identical machine, with the only difference being that the Hitachi machine has a capacity of 16 digits. This Hitachi calculator was designated as the ELCA 46. A slightly modified version of the ELCA 46, the ELCA 46R (as seen below), replaced the [M2-] key with a key for the square root function. Hitachi's ELCA ELectronic CAculators were sold in Asian and European markets.

The Hitachi ELCA 46R
Image Courtesy Takaharu Yoshida

The 1118 uses virtually identical cabinetry and chassis to its slightly less capable and less expensive stable-mate, the Friden 1117. The only real differences in the cabinet are in the cutouts in the keyboard panel for the extra keyboard functions available on the 1118.

The lower half of the cabinet is made of heavy plastic, with the upper half of the case made of a combination of metal, brushed aluminum, and plastic. Inside, the machine is very similar to the EC-1117. It is very likely that the basic design of the EC-1117 and EC-1118 (along with their Hitachi ELCA counterparts) are very similar, with the differences being in the number of Nixie tubes populated, keyboard keys and wiring, and certain chips in the chip set which are replicated to provide additional digits of capacity and function. The eleven LSI chips used in the EC-1118 are all in ceramic packages, with part numbers HD3201, HD3202, HN3202, HD3203, HD3204, HD3206, HD3207, HD3208, and HD3209. There are three of the HD3206 chips used, which gives a clue that the HD3206 chips are those that store the working registers of the calculator, and are likely shift registers that contain 72 bits, or the equivalent of 19 decimal digits. In the 14-digit EC-1118, 8 bits of the 72 bits are unused, leaving the 68 bits, or 16 digits of capacity. The extra two digits are used for keeping track of the decimal point position, and the sign of the number. It is likely that the HD3206 chips contain two such registers each. Three registers would be needed for the working registers of the machine, and two would be required for the two memory registers, totalling five registers, which would take three of the chips, with one register unused in one of the chips. This is just a guess, but from looking at the circuit boards, it seems likely to be relatively accurate. Unfortunately, there has been no luck in tracking down data sheets or pin-out information for Hitachi's LSI calculator chip sets from the late 1960's and early 1970's. Though a square root key is not provided for on the keyboard, the chip set used in the 1118 is capable of carrying out the square root function. Along with the LSI chips, there are a few Hitachi small-scale IC devices used, likely for clock generation and other miscellaneous logic.

Friden 1118 Internal View

The 1118 has a classic Nixie tube display, but uses a smaller tube than the Hitachi CD-79 used in the 1113, 1114, 1115, and 1116 machines. The smaller Nixie is also made by Hitachi, and has part number CD-90. Each of the 14 CD-90 tubes in the machine contains the digits zero through nine and a right hand decimal point. The Nixies are soldered directly to the main circuit board, and are mounted in a rubber shock-mount frame to align and protect the tubes. The Nixie tubes are multiplexed, and are driven by hybrid integrated driver devices. To the right of the Nixies is a set of four indicator lamps that provide sign, overflow, and memory active indicators. The two memory active indicators light up when its corresponding memory register contains a non-zero value, letting the operator know that the indicated memory register is in use.

A Closer View of the Singer/Friden 1118 Keyboard

Operationally, the 1118 is a pretty straightforward four-function desk calculator. The basic four math functions operate as usual for the Singer/Friden machines, with arithmetic mode addition/subtraction, and multiplication and division entered algebraicly. The [R] key swaps the operands of multiplication and division expressions. The [C] key clears the whole machine with exception of the memories, and [CE] clears the display only. A ten-position rotary switch selects the fixed-decimal point location, from zero through nine digits behind the decimal point. The decimal point setting selects the maximum number of digits behind the decimal point. In cases where there are fewer digits behind the decimal point, the calculator will override the setting, reducing, the number of digits displayed behind the decimal point, to avoid causing an overflow. A slide switch selects the rounding mode of the calculator, with positions for force up, truncate, and 5-up/4-down rounding. The 1118 has two independent memory registers, each with their own M+ and M- keys to add or subtract the content of the display to/from the memory register. Each memory also has two two memory recall keys, one which leaves the memory register intact ([S₁] and [S₂]), and the other that recalls the memory register to the display and clears the memory register ([T₁] and [T₂]).

Two annunciators labeled "M₁" and "M₂" at the right end of the display indicate when the corresponding memory register has non-zero content. A rotary switch (the knob closest to the display panel) controls the memory accumulation and constant functions. Settings exist for no constant/sum functions; automatic accumulation of products/quotients in Memory register 1, constant multiplication/division, accumulation of products/quotients in Memory 1 with constant, and automatic accumulation of products/quotients in Memory 1 with accumulation of multiplicand/dividend in Memory 2.

Along with the memory status indicators, two more indicators provide additional status information. One lights if the number on the display is negative, and the other, labeled "UDF" is the error/overflow indicator. On overflow conditions, the UDF lights, but does not cause the machine to ignore key-presses as many calculator do. Calculations may continue, though the results may prove less than useful. The only operation that seems to cause the keyboard to be ignored is division by zero, which lights the UDF light and puts the calculator into an infinite loop trying desperately to solve a problem that can't be solved.. Pressing [C] in this case unlocks the machine. The UDF indicator also doubles as a "busy" indicator, briefly lighting during the time that a calculation is occurring. The EC-1118 performs the all-nines divided by one benchmark in just over 1/3 second.

In November of 2008, a large amount of Friden documentation came into the possession of the Old Calculator Museum, thanks to the generosity of Mr. Roger Rueff, whose father was a Friden service technician during the 1960's and 1970's. While going through this material, a Singer/Friden Electronic Calculator Service Letter (No. 02, Dated 2/3/1972) states that, upon customer request, any of the function keys on the 1118 can be changed to provide the square root function. The change involves moving a wire on the keyboard connector for the function that is selected by the customer to be replaced with the square root function (typically one of the memory function keys, for example [M2-], to an unused position on the circuit board that activates the square root function. This change could be performed in the shop, or at a customer location by a Friden service technician. Time billed for the change is 1/4 hour, and parts involve a new key cap that has a square root symbol on it, which simply replaces the repurposed function key.