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Friden/Singer EC1113 Calculator

Updated 12/29/2015

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. Apparently this machine was built during a time when Singer had not yet completely switched all Friden products to be badged "Singer/Friden Division".

The Friden EC1113 Opened Up

The 1113 is built from five circuit boards which plug into a hand-wired backplane. The boards stack vertically 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 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 that do not appear to be faults with the circuitry, but rather, design compromises. This assumption is made because the same behaviors have been found on another EC1113 that a fellow collector owns. The machine does not generate a correct result on division problems which have a dividend with a digit in digit position 12. 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. Along with this odd behavior, the machine also appears to have rather poor power-on initialization. Frequently when powered up, the display will contain gibberish, with multiple digits lit up at once on the Nixie tubes, 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 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 garbage in 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

An 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. There is no indicator to show when the memory register contains a non-zero value. The 1113 is measurably slower than its successors in the 111x line of machines. It takes about 1 second to calculate the quotient of eleven 9's (remember, the machine gives incorrect results if the 12th digit is used in division calculations) divided by 1. Multiplication of 99999 by 99999 takes about 1/2 second.


Text and images Copyright ©1997-2015, Rick Bensene.