Calfax 890P

Calfax 890P Calculator

The Calfax 890P is a handheld calculator from 1975. It measures approximately 69-77mm wide, 140mm high, and 35mm deep. Weighing 104 grams without batteries, the 890P has an angular two-piece plastic case in black and white. The top section holds the 9V battery and has a metallic brand sticker. The keys are bold colored plastic with a soft click, and the front panel has white printed labels.

The 890P uses a 9V battery or AC adapter and has an 8-digit red LED display, but no ninth digit. Functions include the four standard operations, percentages, and a constant. The 1975 price was $13.88.

Inside, the 890P contains a 42-pin Rockwell processor chip, logic chip, LED display, 20 transistors, 2 diodes, 17 resistors, and 5 capacitors. Two circuit boards are connected by a ribbon cable.

In use, the C/CE key can clear the last entry or the whole calculator. Input overflow is suppressed after 8 digits. Negative numbers display a minus symbol but allow full 8 digit entry. Divide by zero locks up the calculator but is recoverable. Percentages divide the current number by 100.

The case design suggests it was a generic shell used across models. The 890P has some quirks like losing the negative sign and fixed decimals, but works reliably. Likely it was just packaged in bubble wrap originally, not a custom case.

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