h. The head wheel which holds the heads was generally 2 inches in
diameter and rotated vertically 240 revolutions per second. Each head would
record 16.4 lines of video information on each video track. Since there are
525 lines to a frame, the head wheel had to lay about 32 video tracks on the
video tape to get one frame. This quad-head recording system was the first
type of recorder to be used commercially.
But because of their size,
expense, and the equipment required to operate them, the industry that did
use them was the television broadcast station.
They are what is termed
reel-to-reel machines which used 2-inch video tape (fig 1-1).
Figure 1-1.
Quad-head recording system
i. As the broadcast television was developing prior to the early 1960s,
so was another area of television production, nonbroadcast television.
Nonbroadcast A is that area which is made up of educational TV, industry,
and others.
By 1960, nonbroadcast TV had come to the point where the
industry had developed a need for the good but small VR, combining the
newly-developed transistor with some video head design changes. It was not
exactly broadcast standards like the quad-head system, but it was
satisfactory for most nonbroadcast use.
4.
Helical scan system.
The first helical scan system was reel-to-reel
and offered some distinct advantages. It was smaller and more portable than
the quad-head VRs. It used 1/2-inch tape which was put on smaller reels and
thus was easier to handle and take on location.
a. The helical scan VRs got their name from the way the videotape was
wrapped around the head drum which surrounded the rotating head. The tape
was wrapped in the form of a helical or spiral around a cylinder. You will
note that the tape starts at the low end of the cylinder and comes off at
the top end (fig 1-2).
The video tape is never completely wrapped around
the drum, but may look like one of the two views of the drum in Figure 1-2.
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