Sony BVU-950 - Page 27

According
to
NTSC
standards,
nine
horizontal
lines
during
the
i
blanking
period
are
divided
into
half
lines.
As
you
can
see
in
Chart)
4-A,
the
odd
field
ends
in
a
half
horizontal
line,
while
the
even
field
ends
on
a
full
horizontal
line.
Our
framing
servo
utilizes
this
fact
to
identify
the
frame.
A
Syne
2?
VD
C
F
.
r
-
eé.
|
renc
Video
in
Sep.
Detect
PoE
h™"
CTL
&
Servo
Referen
Reset
v2u
|”
E
PT
Reject
|
Gate
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B
Even
Field
——ems-—
Odd
Field
weet
EVEN
Field
c “[ [T YT YT pS |
] OOM ATT
E
)
i
!
{
Even
Even
{
©
TT
|
oa
|
seme
Odd
~
Reference
for
Servo
Chart-4
The half horizontal line reject circuit puts out a series of positive
going pulses at the same rate as the horizontal line scan timing. This
series of pulses is shown in Figure D.
The Gate circuit compares the phase of the vertical sync pulses com-
ing out of the Vertical Drive Detector we mentioned earlier, with
those pulses coming out of the half-horizontal line reject circuit.
It chooses the negative-going pulse of the Vertical sync to examine.
When the negative-going pulse occurs, the gate checks to see if the
4-11