User`s guide

Some third-party MultiSync monitors will work on the Mac/VGA and IIgs, but these
are very rare now. Most MultiSyncs do not go as low as 15 kHz.
"15 kHz" and "30 kHz" refers to the horizontal scan frequency - Apple II video
output has a horizontal retrace roughly 15,000 times per second.
Vertical retrace is a different issue (it is much slower - usually 50 to 100
retraces per second), and most monitors are very flexible in the supported
vertical retrace rate, as far as I know.
This is also where "interlacing" comes in. Interlacing is a technique which
doubles the effective vertical resolution of the monitor, by performing two
vertical scans (fields) per frame, with a slight vertical shift in the second
field. The scan lines for the second field are interleaved between the scan
lines for the first field.
An interlaced display has more noticeable flicker than a non-interlaced display
with double the frame rate, because the phosphor is only lit half as often.
For example, the Second Sight card will support a 400 line interlaced mode with
the IIgs RGB monitor. There will probably be noticeable flicker in this mode
(especially out of the corner of your eye).
This mode will have 60 fields (i.e. 30 frames) per second, whereas the standard
IIgs video output is non-interlaced with 60 frames per second (but only 200
lines vertical resolution).
(I'm assuming 60 Hz mode - the IIgs also support 50 Hz mode, for use in
countries with 50 Hz mains supplies and TVs.)
Television also uses interlacing - with NTSC, there are 525 lines per interlaced
frame and 30 frames per second, with alternating lines being scanned on each
pass of the electron beam (262.5 lines per field, 60 fields per second).
PAL uses 625 lines per frame, usually at 25 frames per second (312.5 lines per
field, 50 fields per second).
______________________________
From: Rubywand
025- Can I replace my GS RGB monitor with one from a PC?
Modern PC monitors generally have a Horizontal scan rate which is too high
to be compatible with the GS. For some replacement options, see Q&A 015 above.
______________________________
026- What are the specs and pinout for the GS RGB
monitor?
Max Resolution: 640 Horizontal dots x 200 Vertical dots/lines
Dot Pitch: .37mm