TV test pattern tube

This tube was used to generate a TV test pattern. Its construction is similar to an ordinary black-and-white picture tube, but instead of the screen, an aluminium plate with an image printed with non-conducting ink is placed inside. The electron beam is scanned across the plate and its current varies according to the amount of ink. In the past, this was a very important component of a TV studio. The TV programme was not broadcast during the whole day and the test pattern was transmitted during programme pauses. The TV owners could set their receivers using the test pattern, also the TV repair shops needed it. One could use it to set picture geometry, brightness and contrast, check beam sharpness and the performance of the high-frequency circuits of the receiver. Later, color test patterns were generated electronically and could be used to adjust color decoders, picture tube color purity etc..