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Fig. 9.
Camera control unit.
the monitors is switched to a point ahead of the output stage. This switch can be used in case of trouble at the camera to prevent the switcher operator from putting the camera on the air. It may also be used with a ready-light system to provide the director with an indication of camera availability.
The camera vertical sweep circuit is contained in the camera control unit, reducing the circuitry required in the camera and at the same time making the camera vertical-sweep control available to the camera control operator. The sweep circuit employs sufficient feedback to eliminate the need for a vertical linearity control. The feedback maintains vertical linearity to well within ±1%.
Control over camera horizontal-sweep amplitude is also available at the camera control unit as is an "overscan" switch
which provides a 5% increase in camera sweep amplitudes. The overscan switch makes it quite simple to overscan the target during rehearsal, thus effectively increasing the useful life of the image orthicon.
The picture monitor uses a type 8AP4A cathode-ray tube. The type 8AP4A was chosen because of its light weight and its high ratio of useful picture area to tube size. It presents a picture only 1 5% smaller than that presented by a 10-in. tube, yet is 2 in. smaller in diameter, thus providing an excellent compromise between the needs of studio and field uses.
Picture monitor vertical and horizontal-sweep circuits provide linearity of better than ±1%. The vertical circuit employs feedback to provide excellent long-term stability. A separate pulse type high-voltage supply, identical with that
L. L. Pourciau: Television Camera
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