12.5) What kinds of monitors can I use with my Atari?

In general, you either need a Composite Video monitor, or a standard TV.

Television:
You'll need a video cable (not detachable on the 400/800), and a TV Switch
Box. Used with VHF Channel 2 or 3.

Monitor:
The 8-bit Atari produces a color Composite Video signal, plus
separate chroma (color) and luminance (brightness) signals which the best
composite video monitors can take advantage of.  Popular examples of such
monitors include the Commodore 1702 and 1804 (and many others).

The pinout of the Monitor port is in the pinout section of this FAQ list.

Gotcha's:

-the 400 and North American 600XL lack a monitor port entirely.  They can only
be used with a TV.

-the 800XL lacks separate chroma/lumi (can be added via hardware modification)

-the XE Game System provides an RCA-style jack in place of the Monitor port;
 so it provides Composite Video but lacks separate chroma\lumi signals

-the XEP80 Interface Module produces a monochrome Composite Video signal via
 an RCA-style jack.  This higher-resolution signal produces crisp, clear 80
 column text on 80-column monochrome composite video monitors.

Jerry Jessop, mailto:jjessop1@home.com explains why French Ataris produce
fewer colors:

"I will tell you why it only has monochrome out, because it's SECAM and
a SECAM GTIA was never produced. The PAL GTIA is used in France and
the Lum outputs are run into an onboard encoder to produce a "psudo"
color depending on the Luminance output, composite only. This is why a
SECAM VCS or 800 has nowhere near the same number of colors (16)
availible as a PAL or NTSC unit (256).

The FGTIA was never completed as the market size did not warrant the
expense. The largest SECAM market is not France but the Soviet Union
(former) and in 80-84 sales of these items there were not possible."