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Friden/Singer EC1113 Calculator
Updated 8/15/2000
The Friden/Singer EC1113 is a very early MOS IC-based electronic calculator. The EC1113 is a 12-digit Nixie tube display, four-function office calculator with a single memory register. The majority of the logic of the machine is made up of early Hitachi MOS 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 all IC-based calculators in the museum. This machine definitely predates its stable-mate machines, the Singer/Friden 1114 and Singer/Friden 1115, which are machines of very similar appearance, function and design, but were made with slightly newer technology. 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 as the Singer buy-out of Friden was being implemented, and for market continuity or political purposes (hard to say which), it was decided to put the Friden name on this machine, and switch over to the Singer name on later machines. As with the other machines in the EC111X series, the 1113 was obviously farmed out to Hitachi for design and manufacture, as nearly every part in the machine, including the circuit boards themselves, are made by, and carry, Hitachi logos.
The Friden EC1113 Opened Up
Mechanically, the 1113 is virtually identical to its slightly younger sibling, the 1114. 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 which 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. The 2nd board contains the display subsystem, including the 12 Hitachi-made CD 79 Nixie tubes and their associated driving circuitry, which is made of mostly discrete components. The remaining three boards make up the calculating logic of the machine, and are populated a total of 108 early Hitachi MOS IC's in metal can packages, with each device having 12 pins. The part numbers of all of the IC's in the machine are of the form HD7xx, with the full compliment of devices used in the machine 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, which indicates to me that there were some rather significant logic design changes between the 1113 and the later machines in the series.
A Closer View of the EC1113 IC's
There are some quirks with the operation of the machine which do not appear to be faults with the circuitry, but rather, design compromises or outright design errors. This assumption is made because the same behavior was 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 which 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 bizarre 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 gibberish. Pressing "CM" followed by "C" after powering up assures that this hash 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 very 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 'sigma' key allows for 'sum of products or quotients' to automatically accumulate in the memory register. The 1113 lacks a "Clear Entry" key, opting instead for a 'back space' key which allows entered digits to be erased digit at a time. This is unusual, and may be the only Friden/Singer of this vintage which has this function -- all of the other 111X machines opt for a "Clear Entry" type function to allow the user to correct mistaken input.
A View Showing the Hitachi CD79 Nixie Tube Nomenclature
An neon annunciator at the left end of the display indicates Overflow condition. A similar annunciator 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 times 99999 takes about 1/2 second.