The transmitted V I T S has a specific frequency,
amplitude and waveform as shown in Fig. 14. Television
networks use precie signals for adjustment and checking of
network transmission equipment, but the multi-burst signal
in VITS can also be used for checking the operating
condition of TV sets. The first frame of VITS at the " B "
section (line 18) in Fig. 14 begins with a white reference sig-
nal, followed by sine wave frequencies of 0.5MHz, 1 .OMHz,
2MHz, 3MHz, 4.0MHz and 3.58MHz. This sequence of
frequencies is called a "multi-burst" which is very useful.
F I E L D 1
(MULTI-BURST)
F I E L D 2
F I E L D 1&2
Fig. 13. V I T S signal, Fields
1
and 2
The VITS other than the multi-burst signal is different
depending on broadcast station. VITS staircase waveform
containing a 3.58MHz burst signal is valuable to the
network, but has less value to the service technician. A s
Field 1 is interlaced with Field 2, line 17 is followed by line
279 and line 18 is followed by line 280. The entire VITS
appears at the bottom of the vertical blanking pulse and just
before the first line of the video signal.
Each of the multi-burst frequencies is transmitted at
equal strength. By observing the comparative strengths of
these frequencies after the signal is processed through the
television receiver, the frequency response of the set can be
checked.
All multi-burst frequencies are transmitted at the
same level, but will appear as shown in Fig. 14 even on a
good color television set, due to its response curve; showing
the allowable amount of attenuation for each multi-burst
frequency. Remember that — 6dB equals half the reference
voltage (the 2.0MHz modulation should be used for
reference).
15
NO.18
-HORIZ. S Y N C . P U L S E
V E R T I C A L B L A N K I N G I N T E R V A L
(NO 1 ~ N021)
L I N E NO.17
3,58MHZ
NO 279
NO 280
• V E R T I C A L B L A N K I N G I N T E R V A L
(NO 263 ~ NO 282)
( M U L T I - B U R S T )
0,5 1 2 3 3,58 4,2
MHZ
NO 17
NO 279
N018
NO 280
RESPONSE-d
B
F R E Q U E N C Y — M H z
Fig.
14. Color T V I F amplifier response curve
