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Poking contacts on an LCD display with a battery wire causes segments to distort and produces audible signals from the display's own oscillator

Procedure L3Craft E · Modular, Eurorack, grooveboxes & dawless

An LCD (liquid crystal display) uses a built-in oscillator to drive the crystal cells. Touching the LCD’s row/column contact strip with a battery wire directly interferes with the timing circuit, causing segments to display incorrectly and producing audible clicking, buzzing, or tonal sounds from the display oscillator — sounds Collins calls ‘an eerie audio/visual feedback loop.’ The technique requires finding the contact points (typically rubber strips pressed under the glass edges) and probing with a wire connected to a 1.5V cell. Different contact pairs produce different patterns and sounds. The display functions as a combined audio/visual instrument, where what is seen encodes what is heard and vice versa. Commercial LCD hack kits expand this into full circuits.

Examples

Probe calculator LCD contacts with a battery wire; the display shows corrupted numerals and simultaneous beeps/squeals appear through an attached amplifier. Different pairs of contacts produce different segment patterns and different pitches.

Assessment

What is producing the audio signal when you hack an LCD display? Why does the visual corruption and the audio signal change simultaneously when you move the probe wire?

Prerequisites — understand these first

Sources

“Locate the connections to the LCD—usually these are tiny dark points embedded in a rubber strip pressed under either edge of the glass, but sometimes they are larger metal tabs.”
corpus · nicolas-collins-handmade-electronic-music-the-art-of-hardwar · chunk 40

Taught in modules