The Display Cards 8*24 and 8*24 GC do not use software for switching to the
NTSC interlaced mode. To put the Display Card 8*24 into the NTSC mode, a
properly configured cable is all that is required. Most NTSC devices use an
RCA-type phono-connector, so this diagram uses that as a reference point.
Adjust the phono-connector side to whatever type of connector is used. "Tip" is
the pin in the center of the connector (the signal); the sleeve is flanged
around the outer edges of the connector (the chassis ground).
Card Connector RCA-Type Phono-Connector
-------------- ------------------------
4 MON.ID1 (sense0) --|
7 MON.ID2 (sense1) --|
11 C&VSYNC.GND --------|
5 GRN.VID -----------------> Tip (signal)
Shell CHASSIS.GND --------------> Sleeve (ground)
By grounding pin 4 and pin 7 to pin 11, the video cards are told that an
interlaced (NTSC) monitor is attached. The actual black and white video signal
is on pin 5 and connects to the center (Tip) of the phono-plug. The shell of
the card connector connects to the sleeve of the phono-plug.
To acquire a color NTSC signal from any Apple Macintosh display card, an
RGB-to-NTSC converter is required.
For more information, search under "NTSC video encoding".