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<p>and <a href="page.php?w=Photoelectric_sensor">photo sensors</a> to optically detect actuated keys. Most commonly the emitters and sensors are located in the perimeter, mounted on a small <a href="page.php?w=Printed_circuit_board">PCB</a>. The <a href="page.php?w=light">light</a> is directed from side to side of the keyboard interior and it can only be blocked by the actuated keys. Most optical keyboards require at least 2 beams (most commonly vertical beam and horizontal beam) to determine the actuated key. Some optical keyboards use a special</p><p>
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