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2-4 Chroma ID
The identification
of a colour
or black/white
broadcast
is achieved
by sensing
the voltage
level input at pin 18. This voltage
is supplied
from pin 26
of ICI 01 through the
inverter
circuit,
Q771. When there is a black/white
broadcast
the voltage
on pin 26 goes low.
Normally,
pin 26 operates
as colour control function, and the control voltage is from pin 4 of
the CPU.
To
identify
the colour
system
during
a black/white
broadcast,
the CPU judges
that the system
is NTSC when the following conditions are detected at same time.
(1) The colour system is "AUTO" or "NTSC" system.
(2) The field frequency is 60 Hz.
(3) TV/AV mode is "TV" mode.
CPU
18
CHROMA ID
btE!zzd
4
COLOUR
R773
10k
R774
220k
4
R775
12k
1
"T
U
.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
i Colour control
~ D/A circuit
~
....................................
ICI 01
Chroma/Def.
26
COLOUR
2-5 Ident (Identification)
The identification
of the receiving signal status is done by the CPU sensing the voltage level
at the input pin 15, as shown below. The ident signal is presented at pin 4 of IC101 and fed to
pin 15 of the CPU through the converter circuit consisting of Q700, R706 and R722.
When the CPU judges that the system is 4.43MHz,
it outputs a "Low" signal from pin 39 to
select the PAUSECAM
system.
CPU
IDENT 15
4.5 MHZ 39
0
12V
I
ICI 01
Chroma/Def.
,
Pin39
Pin15
Judgement
Signal status
L
O-1.8V
4.43 MHZ
No sync.
H
1.8V - 4.3V
3.58 MHz
Signal present
L
4.3 v -
5.OV
4.43 MHZ
Signal present
AA1-A
AAl -A
-13-
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