Sharp DV-SV 80 H, Service Manual

Page: 12 / 28

12
Fast Blanking
75R input and output impedance. This control voltage allows devices to over-ride the composite video input with RGB inputs,
for example when inserting closed caption text. It is called fast because this can be done at the same speeds as other video
signals, which is why it requires the same 75R impedances.
0 to 0.4V : TV is driven by the composite video input signal (pin 19). Left unconnected, it is pulled to 0V by its 75R
termination.
1V to 3V : the TV is driven by the signals Red, Green, Blue and composite sync. The latter is sent to the TV on pin 19.
This signal is useful when using a TV to display the RGB output of devices such as home computers with TV-
compatible frame rates. Tying the signal to 5V via 100R forms a potential divider with the 75R termination,
holding the signal at around 2V. Alternatively, if a TTL level (0 to 5V) negative sync pulse is available, this will
be high during the display periods, so this can drive the blanking signal via a suitable resistor.
Control Voltage
0 to 2V = TV, Normal.
5 to 8V = TV wide screen
9.5 to 12V = AV mode
12.2. CABLE DIAGRAM
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