In the early 1970s, the emergence of LED display technology enabled the creation of the first handheld electronic calculators. Companies raced to develop and market these novel devices to consumers and businesses. One such calculator was the Ajax 2500, released around 1974-1975 by the British company Acme Electric.
With its sleek and stylish design, the Ajax 2500 exemplified the aesthetics of 70s consumer electronics. The case consisted of silver and black plastic pieces with a raised upper section prominently displaying the “Ajax” brand name. The keys were brightly white with a loud, positive click when pressed. Behind the steeply angled red filter sat the key feature – an eight digit LED display plus an additional digit for signs and status indicators.
Despite its diminutive size of 3” wide x 5.5” high, the Ajax 2500 packed useful functionality. It performed the four basic arithmetic operations and had a percent key and three-function memory. The logic handled features like automatic constant, chaining, and full eight digit negative numbers. While overflow was indicated, the calculator had no error recovery. The memory system, accessed via the M key, was basic but practical.
Inside the tidy case, electronics construction was quite manual. The main logic board was secured by melted plastic lugs, as was the LED display module. Wiring between boards used individual color-coded wires. The Spartan circuitry consisted mainly of a Mostek MK5022 CPU chip, driver chip, transformer, and other discrete components.
From the signatures on the chips, the Ajax 2500 dates from around week 20 of 1974. It owes its design to Radofin, as the circuit board markings reveal. Ajax represented a branded version manufactured for the British company.
With its smooth case lines, bright crisp display, and clicky keys, the Ajax 2500 brought satisfying tactile interaction. It delivered useful functionality in a stylishly compact package. For the time, this battery-powered handheld calculator provided portability, convenience and performance. The Ajax 2500 stands as an icon of the emerging consumer digital age.
