The building uses photocells and motion sensors for general lighting. On the roof, sensors with hemi-spherical lens acts as photocells, monitoring the intensity of lights. It contained two optical telescopes with two photocells. By the mid-1930s, selenium photocells controlled assembly lines, elevators and looms. The circuits overcame the image-destroying lag effect that is part of selenium photocells. Selenium is a semiconductor and is used in photocells. Similarly, he developed tactile devices powered by photocells that enabled the blind to sense light. The track has 16 turns and contains 24 photocells for timekeeping. These floods simply overwhelmed Kell's imaging photocells. After the 1950s selenium in photocells was gradually replaced by CdS and CdSe. At the finish line, photocells and digital cameras are used to establish the placings. The tubes were made from NMR tubes and the current came from CdS photocells. These experiments have been used to develop better photocells and thin films. The success of sound films stimulated the search for new applications of photocells. The satellite motion and rotation caused the photocells to scan the Earth in successive "lines".