Editing Test card (section)

==Monoscope==
{{multiple image
| align = right
| direction = vertical
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| image1 = Monoscope.jpg
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| caption1 = A [[monoscope]]
| image2 = MonoscopeCU.jpg
| width2 = 300
| caption2 = Close-up of the test-card image from a monoscope
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{{main article|Monoscope}}

Rather than physical test cards, which had to be televised using a camera, television stations often used a special purpose camera tube which had the test pattern painted on the inside screen of the tube. Each tube was only capable of generating the one test image, hence it was called a [[monoscope]].

Monoscopes were similar in construction to an ordinary [[cathode-ray tube]] (CRT), only instead of displaying an image on its screen it scanned a built-in image. The monoscope contained a formed metal target in place of the phosphor coating at its "screen" end and as the electron beam scanned the target, rather than displaying an image, a varying electrical signal was produced generating a video signal from the etched pattern. Monoscope tubes had the advantage over test cards that a full TV camera was not needed, and the image was always properly framed and in focus. They fell out of use after the 1960s as they were not able to produce color images.
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