The Commodore LC925 is an arithmetic calculator with eight-digit precision and algebraic logic. It has eight functions, 26 keys and is powered by two AA 1.5V batteries.

This calculator has a second-generation twisted nematic (TN) LCD (liquid crystal) with yellow filter display, which were first introduced in 1975. The first-generation Dynamic Scattering Mode (DSM) LCDs first appeared in 1971-72, where the liquid crystal was normally clear but turned opaque white when a voltage was applied. The displays of calculators using DSM LCDs required built-in side lighting, which removed much of the advantage of low power consumption of the LCD.

The TN LCD with yellow filter did not require illumination as the liquid crystal assembly is held between crossed polarising filters. With no voltage applied the liquid crystal rotates the polarisation of light so that it passes through the filters and shows the reflective surface behind. When an appropriate voltage is applied the liquid crystal stops rotating the plane of polarisation of the light and that region appears black. As a result the power consumption is very small. The yellow filter helped to remove damaging UV light.

This LC925 calculator is believed to be the earliest example of a calculator with an LCD screen in our collection.

Manufacturer: Commodore
Date: 1975

This exhibit has a reference ID of CH48150. Please quote this reference ID in any communication with the Centre for Computing History.

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