The Elka 101 calculator, introduced in 1973,was manufactured by ISOT in Bulgaria. It has bold design aesthetics and typical technological capabilities of the early 1970s. It stands out from other calculators with its vibrant color scheme and distinctive design features.
The Elka 101 is compact, measuring approximately 70mm x 136mm x 30mm (width, height, depth), and weighs 126 grams without batteries. It is powered by four AA batteries, providing 6.0V DC. Notably, it does not support an adaptor, but it includes a convenient yellow ribbon to aid in battery removal. If the voltage drops below 4V, the calculator displays all decimal points as a low power indicator.
The calculator’s case is available in yellow, green, or orange, with a smooth rear and a slightly matte black front. The front panel features a brushed aluminum strip with black printed text surrounding the switches. The top of the calculator is raised by about 30 degrees, with the orange display filter elevated further, showcasing a “fine-line” design. The lower front edge is adorned with the brand and model number in white, typical of 70s design trends. The keys have a bouncy feel and produce a slightly hollow sound when pressed.
The display is an 8-digit red LED with a bubble lens, including a ninth digit for the minus sign, error indications, and memory flag. The Elka 101 offers basic four-function capabilities with percentages and a two-function memory. A switch allows for toggling the accumulator memory on or off.
Under the hood, the Elka 101 is equipped with a Rockwell A1030PE CPU, manufactured in the 23rd week of 1974. The main board also includes two Texas SN75492AN logic chips, 11 transistors, 10 diodes, 9 resistors, 5 capacitors, and a transformer. The keyboard assembly features a 5-digit and a 4-digit red plastic bubble lens LED unit, along with additional diodes and resistors. The small CPU board is connected to the full-sized keyboard and display board via a 29-way ribbon cable, with the assembly secured using the case fixing screws. Disassembly is straightforward: removing four screws on the back (two hidden inside the battery compartment and two under the bottom rear label) allows the case to separate easily.
Logic
- The (C) key cancels the last number entered on the first press and clears the calculator on the second.
- Input overflow is suppressed; keying in a nine-digit number ignores the ninth digit.
- The calculator uses reverse polish notation logic. For example, to calculate 5-3, you would key in (5)(+)(3)(-) to get “2”. The equals key is only used for multiply and divide operations, making this a semi-RPN calculator.
- Overflow shows the result and “C” (“E” if negative) in the far left (ninth) digit and is recoverable using (C).
- Divide by zero shows zero and “C” in the far left (ninth) digit and is recoverable using (C).
- There is automatic constant on multiply and divide only.
- The memory on switch puts the calculator in auto-accumulation mode, adding every result of equals to the memory.
- Memory store is indicated by the decimal point of the far left (ninth) digit, referred to as “memory busy” in the manual.
- Overflow in memory is flagged, is recoverable, and stores the shifted result.
- The calculator has a pseudo fixed decimal bug. For example, keying in (1)(+)(0)(.)(0)(0)(0)(+) results in “1.000,” which remains a fixed three decimal point number until an answer requires more digits.
Marketing quote from Elka: “Your ELKA 101 8-digit pocket calculator is light and compact. You can take it anywhere with you. But with its universal applications, high speed and high reliability, it is comparable with machines that are much larger and more expensive.”
The Elka 101 calculator is a unique piece of technology from the 1970s, known for its bold colors and semi-RPN logic. Despite some quirks, such as the pseudo fixed decimal bug, it offers a solid, functional design with a clear red LED display. The text on the aluminum strip is prone to wear, and the original case is a soft black plastic with a three-quarter side and top zip.
