When TV first came out how many hours was it on for?

in 1884 Paul Gottlieb Nipkow, a 23-year-old university student in Germany, patented the first electromechanical television system which employed a scanning disk, a spinning disk with a series of holes spiraling toward the center, for rasterization. The holes were spaced at equal angular intervals such that in a single rotation the disk would allow light to pass through each hole and onto a light-sensitive selenium sensor which produced the electrical pulses. As an image was focused on the rotating disk, each hole captured a horizontal "slice" of the whole image.

Nipkow's design would not be practical until advances in amplifier tube technology became available. The device was only useful for transmitting still "halftone" images-represented by equally spaced dots of varying size-over telegraph or telephone lines.[citation needed] Later designs would use a rotating mirror-drum scanner to capture the image and a cathode ray tube (CRT) as a display device, but moving images were still not possible, due to the poor sensitivity of the selenium sensors. In 1907 Russian scientist Boris Rosing became the first inventor to use a CRT in the receiver of an experimental television system. He used mirror-drum scanning to transmit simple geometric shapes to the CRT