loscope control setting for viewing the alternate
V I T S .
Most network television signals contain a built-in
test signal (the V I T S ) that can be a very valuable
tool in troubleshooting and servicing television
sets. This V I T S can localize trouble to the antenna,
tuner, IF or video sections and shown when rea-
lignment may be required. The following procedu-
res show how to analyze and interpret oscilloscope
displays of the V I T S .
The V I T S is transmitted during the vertical blanking
interval. On the television set, it can be seen as a
bright white line above the top of the picture, when
the vertical linearity or height is adjusted to view
the vertical blanking interval (on TV sets with inter-
nal retrace blanking circuits, the blanking circuit
must be disabled to see the V I T S ) .
The transmitted V I T S is precision sequence of a
specific frequences, amplitudes and waveshapes as
shown in
Fig.
1 6 .
Television networks use the precision signals for
adjustment and checking of network transmission
equipment, but the technician can use them to eva-
luate television multiburst signal in V I T S can also
be set performance.
The first frame of V I T S at the " B " section (line 18)
in F i g . 1 6 begins with a white reference signal, fol-
lowed by sine wave frequencies of 0.5 MHz, 1.0
MHz, 2 MHz, 3 MHz, 4 MHz and 3.58 MHz. This
sequence of frequencies is called the "multi-burst".
( M U L T I - B U R S T )
3.58MHz
F I E L D I
F I E L D
2
( M U L T I - B U R S T )
0.5 I 2 3 3.58 4.2MHz
F I E L D I
4 2
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Fig. 16 V I T S signal. Fields 1 and 2
17
V E R T I C A L B L A N K I N G I N T E R V A L ( N O : 1 ~ N O . 2 1 )
H O R I Z . S Y N C . P U L S E
L I N E No.17
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No.279
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V E R T I C A L B L A N K I N G I N T E R V A L ( N O . 2 6 3 ~ N O . 2 8 2 )
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