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Sec. 8–9 Television 631<br />

Camera<br />

Target<br />

Raw video<br />

C =m y (t )<br />

m s (t)<br />

Electronic<br />

switch<br />

Composite video<br />

signal out<br />

D =m c (t )<br />

Lens<br />

Sync<br />

generator<br />

B<br />

Sync<br />

Blanking (binary signal)<br />

A<br />

(a) Block Diagram of Camera System<br />

T h =63.5 msec<br />

One line<br />

interval<br />

Video interval<br />

Sync interval<br />

10.5 msec<br />

Blanking<br />

A =Blanking pulse (binary signal)<br />

3 5<br />

4<br />

Boundary for<br />

viewable area<br />

1<br />

6<br />

2<br />

No blanking<br />

Volts<br />

Blanking level<br />

Sync level<br />

Volts<br />

White level<br />

B =sync waveform, m s (t)<br />

C =raw video, m y (t)<br />

t<br />

t<br />

Black level<br />

t<br />

(b) TV Raster Scan<br />

Figure 8–30<br />

Volts<br />

White level<br />

Black level<br />

Blanking level<br />

Sync level<br />

(c) TV Waveforms<br />

1<br />

D =composite video signal, m c (t)<br />

2 3 4 5 6<br />

Generation of a composite analog black-and-white video signal.<br />

1.0 volt<br />

t<br />

interlacing that is used. When the scan reaches the bottom of a field, the sync pulse is widened<br />

out to cover the whole video interval plus sync interval. This occurs for 21 lines, and, consequently,<br />

a black bar is seen across the screen if the picture is “rolled up.” In the receiver, the<br />

vertical sync (wide pulse) can be separated from the horizontal sync (narrow pulse) by using<br />

a differentiator circuit to recover the horizontal sync and an integrator to recover the vertical

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