RS-170 is sometimes described as "the interlaced 60Hz video signal
standard used for broadcast video in America."
This statement is a little misleading. RS-170 has not been the broadcast
video standard in the United States for more than twenty years. RS-170,
drafted in 1957, is a video signal developed by the Engineering Industries
Association as a standard for monochrome (black and white) television
studio facilities.
RS-170 can be recorded using the "Video In" jacks of most video tape
recorders. The Macintosh II Video Card can generate a signal that is very
close to the exact specifications of the RS-170 standard--close enough so
that it can be displayed on most RS-170 monitors, recorded on most RS-170
video tape recorders, and so on. Unfortunately, the minor deviations from
the exact standard causes problems with some video equipment.
Twenty years after the drafting of RS-170, the EIA video signal standard
proposal RS-170A evolved into what is known today as NTSC. NTSC is the
color television standard of the National Television Standards Committee,
and is the standard now used for broadcast video in America. This
standard is the result of combining three RS-170 signals into a single
encoded color video signal.
While RS-170 signals are compatible with most of today's NTSC video
products, it is NOT broadcast video, NTSC video, or color video. Not
knowing this fact can lead to confusion.
For more information, search for "Macintosh and Video Overview".