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Friden/Singer EC1113 Calculator

Updated 6/25/2017

The Friden/Singer EC1113 is an early small scale MOS IC-based electronic calculator. It is a 12-digit Nixie tube display, four-function office calculator with a single accumulator-style memory register. The majority of the logic of the machine is made up of early Hitachi PMOS IC's with date codes from the early part of 1969. Based on other date information in the machine, the date of manufacture appears to be mid-1969, making this one of the earlier IC-based calculators in the museum. The EC1113 was designed and manufactured for Friden by Hitachi in Japan, being the first integrated circuit based calculator made by Hitachi. Hitachi marketed their own version of this machine in Asia as the ELCA-22. The ELCA-22 was introduced in July, 1967, and was introduced by Friden as the EC-1113 in February of 1969. The EC-1113 predates its stable-mate machines, the Singer/Friden 1114 and Singer/Friden 1115, which are machines of very similar appearance, function and mechanical design, but were made with newer technology integrated circuits. Note that this machine has a "Friden" nameplate on the keyboard panel versus the Singer legend on the later machines. This machine was built during a time when Singer had not yet completely switched all Friden products to be badged "Singer/Friden Division". As part of the Singer purchase of Friden, it was decided that it was no longer cost-effective for Friden to continue to design and manufacture electronic calculators in the US. The Japanese had become very adept at design and manufacture of electronic calculators that were significantly less-expensive due to low labor costs and a favorable exchange rate. Friden's new management tested the waters by marketing a transistorized electronic calculator designed and manufactured by Hitachi in Japan, the Friden 1112. The reasonable success of the Friden 1112 made it clear that more money could be made by Friden marketing and supporting calculators designed and manufactured in Japan, and at that point, Friden's management began slowing dismantling its US-based calculator engineering and manufacturing operations in favor of OEM agreements with Hitachi, and later, other off-shore calculator manufacturers. The EC-1113 was the first of a long line of Hitachi-designed and manufactured machines imported by Friden and sold and supported under the Singer/Friden badge.

The Friden EC1113 Opened Up

The 1113 is built from five circuit boards which plug into a hand-wired backplane. The boards stack horizontally inside the machine, arranged in a metal cage that provides shock isolation and stability for the cards. The top circuit board in the stack is smaller than the other boards and provides power supply regulation and filtering functions, as well as containing the master clock oscillator and keyboard input conditioning circuitry. The second board contains the display decoding and driving circuits, including the 12 Hitachi-made CD-79 (early versions of the EC1113 used Hitachi CD-71) Nixie tubes and their associated driving circuitry, which is made of mostly discrete components. The third board contaons the arithmetic unit, along with the accumulator and memory register logic. The fourth board makes up the master control and sequencing logic. The bottom-most circuit card provides major timing control and the display register. The EC-1113 uses a total of 108 first generation Hitachi HD7xx-series PMOS IC's in metal can packages, with each device having 12 pins. The full compliment of devices used in the machine is made up of (with the number devices of each type listed in parenthesis after the part number): HD701 (9), HD703 (17), HD704 (9), HD705 (20), HD707 (5), and HD712 (48).

The Circuit Boards of the EC1113

The EC1113 differs from its later brothers in the EC111X-series of machines by virtue of the fact that it operates with full floating decimal point. The later machines all operate with fixed decimal point positioning.

A Closer View of the EC1113 IC's

There are some quirks with the operation of the machine are faults with the circuitry, but rather are by design to simplify the logic of the machine. The machine does not generate a correct result on division problems which have a dividend greater than 11 digits (including digits behind the decimal point). Performing such calculations results in incorrect answers and false overflow conditions. Also, multiplications that result in products which have more than 11 digits give incorrect answers and false overflow indications. The reason for this behavior is that one digit of the machine's working register is consumed by a special "marker" digit, which consists of all four bits encoding the digit being a '1' (e.g., 1111). This marker is used by the logic to determine when the multiplication or division operation is complete. As a result, one digit of the machine's capacity is "lost" due to this design, causing the unexpected results. The EC-1113 also appears to have rather poor power-on initialization. Many times when first powered up, the display will contain gibberish, with multiple digits lit up at once within a Nixie tube, multiple decimal points on at once, and sometimes the machine will be locked due to a spurious overflow condition. The memory register can also come up with random and sometimes invalid content. Pressing [CM] followed by [C] after powering up assures that this trash is cleared out, and the machine will operate properly. If this isn't done, the random content of the registers of the calculator can lead to strange behavior of the machine until it is cleared properly.

Detailed View of one of the EC1113 Circuit Boards

The memory functions operate as expected, with a [M+], [M-], memory recall ([RM]), and memory clear keys ([CM]). A push-on/push-off [∑] key allows for sums of products or quotients to automatically accumulate in the memory register. The 1113 lacks a "Clear Entry" key, opting instead for a [←] key that allows entered digits to be erased digit at a time. This is unusual, and may be the only Friden/Singer calculator of this vintage which has this function -- all of the other 111x-Series machines opt for a "Clear Entry" function to allow the user to correct mistaken input.

A View Showing the Hitachi CD79 Nixie Tube Nomenclature

As noted earlier, there are two different versions of the EC-1113. The earlier version of the calculator uses Hitachi CD-71 Nixie tubes. At some point fairly early in the manufacturing lifetime of the machine, a engineering change was made to utilize Hitachi CD-79 Nixie tubes rather than the CD-71 devices. There are specialized transistors used on the Nixie display circuit board (marked with a black dot on top of the transistor case) that are specially selected to properly match the characteristics of the CD-71 tubes. The revised version of the Nixie display board replaced the CD-71 Nixie tubes with CD-79 devices, which have different characteristics that no longer required specially selected cathod drive transistors. This change reduced costs and improved the reliability of the display system.

A neon indicator at the left end of the display indicates Overflow condition. A similar indicator on the right end of the display indicates a negative number on the display.

The EC-1113 runs at a master clock frequency of approximately 42KHz. The early Hitachi PMOS integrated circuits used in the calculator are not tremendously fast devices, and thus a conservative clocking rate was used to assure reliability rather than raw speed. This makes the EC-1113 measurably slower than its successors in the 111x line of machines, as Japanese MOS integrated circuit continuously improved. The EC-1113 takes about 1 second to calculate the quotient of eleven 9's (the largest allowable divisor) divided by 1. Multiplication of 99999 by 99999 takes about 1/2 second.

Text and images Copyright ©1997-2017, Rick Bensene.