NTSC/PAL/SECAM/PERITEL

Brief review of analogue television standards

(Presented in order of historical appearance,
sources: Sony & Wikipedia articles about NTSC, PAL & SECAM)

Broadcast television systems (or terrestrial television systems outside the US and Canada) are the encoding or formatting systems for the transmission and reception of terrestrial television signals. NTSC, PAL and SECAM are all colour standards for analog television broadcast.

NTSC
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC) in 1941.
In 1953, a second NTSC standard was adopted, which allowed for colour television broadcast compatible with the existing stock of black and white TV sets.
The NTSC standard was used in most of the Americas (except Argentina, Brazil, Paraguay, and Uruguay), Myanmar, South Korea, Taiwan, Philippines, Japan, and some Pacific Islands nations and territories.
An NTSC picture is made up of 525 interlaced lines and is displayed at a rate of 29.97 frames per second.

PAL
Phase Alternating Line (PAL) is a colour encoding system for analogue television. The PAL format was patented by Telefunken (Hanover, (then West-)Germany) in December 1962.
PAL was adopted by most European countries, by all African countries that had never been a Belgian or French colony, by Argentina, Brazil, Paraguay, Uruguay, and by most of Asia (including the Middle East) and the Pacific.
Countries in those regions that did not adopt PAL were France, most ex-Soviet states, Japan, South Korea, Liberia, Myanmar, the Philippines, and Taiwan.
A PAL picture is made up of 625 interlaced lines and is displayed at a rate of 25 frames per second.

SECAM
SECAM ("Séquentiel de couleur à mémoire", French for "Colour sequential with memory"), is an analog colour television system that was used in France, some parts of Europe and Africa, and most ex-Soviet states.
Development of SECAM predates PAL, and began in 1956 by a team led by Henri de France working at Compagnie Française de Télévision (later bought by Thomson, now Technicolour).
Like PAL, a SECAM picture is also made up of 625 interlaced lines and is displayed at a rate of 25 frames per second.
The black & white television signals of the various European countries were so similar before the creation of the PAL and SECAM colour systems, that PAL and SECAM are in fact based on the same common foundations... except for the way in which PAL and SECAM each process colour information in a different way.
So, in practice, a PAL TV set can display a SECAM picture, but that picture will be black & white. Similarly, a SECAM TV set can also display a PAL picture, but that picture will also be black & white.
NTSC was considered undesirable in Europe because of its tint problem, requiring an additional control, which SECAM (and PAL) solved.

Black and White to colour transition
NTSC, PAL and SECAM are standards that permited existing black and white TV sets predating their introduction to continue to be operated as black and white TV sets. Because of this compatibility requirement, colour standards added a second signal to the basic monochrome signal, which carries the colour information.

Comparison table

{1} PAL M is an exception with 525 lines at 29.97 fps.

Disambiguation: PERITEL

Unlike NTSC/PAL/SECAM, PERITEL is absolutely not a colour standard for analog television broadcast but simply a norm for a connector that carries the various audio and video signals and their control.

Its full name is "Péritélévision". Péritel or PERITEL or SCART^{2}{3} is the name of a 21-pin plug or socket.
Male (plug) on cables, female (socket) on TV sets and other devices that generate or process video (input or output).
PERITEL sockets are originally a French invention. Their use on all TV sets sold in France became legally mandatory at the end of 1979 — an obligation that ended in July 2015. Largely inspired by German DIN connectors, the idea was to carry all the signals needed to connect a TV set to its peripherals in a single cable: external subtitles or teletext decoder, VCR, game console, computer, Canal+ decoder, etc.
PERITEL transports different types of video signals (either in RGB or CVBS mode) with stereo sound, both in input^{4} and output.
PERITEL sockets are compatible with 4:3 ratio (later extended to 16:9 ratio), 50 Hz or 60 Hz, 525-line and 625-line analogue video standards as well as PAL, SECAM or NTSC colour standards.
More information about PERITEL on Wikipedia (EN, FR).

{2} "Syndicat des Constructeurs d'Appareils Radiorécepteurs et Téléviseurs"

{3} PERITEL is also known internationally as EuroSCART, Euroconector and EuroAV or EXT, or EIA Multiport in the US. There is also a Japanese version of this connector, called JP21, which carries the same signals but in a different layout. Therefore, an adapter is needed between PERITEL and JP21 devices.

{4} RGB is limited on the TV set to input only: signal from "video source" to "TV set". RGB entering the TV set, yes. RGB exiting the TV set, no.

In 1982, as the development of a specific SECAM version of the computers (including FGTIA) could not be done overnight, Atari France modified PAL versions of the Atari 400 & 800 models, marketed under the names PERITEL Atari 400 and the PERITEL Atari 800.
This modification consists of an added video circuit which produces an additional RGB signal — very clear but limited to 8 colours — physically conveyed in a PERITEL^{5} plug. Note that the original PAL video signal remains available on the TV antenna plug, as well as on the 5-pin 180° DIN monitor socket of the Atari 800.
Equipped with this PERITEL plug (in RGB mode of course), the natively-PAL computers could display a colour image on a SECAM TV set sold in France.

{5} Either a PERITEL cable directly attached to the computer, or a detachable cable that plugs into a dedicated 8-pin 270° DIN socket on the computer and provides a PERITEL plug at the other end.

Much later, Atari offered computers^{6} in the SECAM colour standard for analog television broadcast, which physically connected to the TV set with a PERITEL plug, but this time in CVBS mode — hence the loss of picture clarity compared to RGB. For example, a SECAM Atari 800XL connected to the TV set of the time also with a PERITEL plug...

{6} See the table below

So, the names PERITEL Atari 400 & 800 are a bit inappropriate. A more accurate name would have been PAL + RGB Atari 400 & 800.
But, well, I can understand the marketing logic. By promoting models with this name "PERITEL", buyers who were not audio/video experts were reassured:
"Oui! I have a PERITEL socket on my TV set, sacrebleu!"

Which version exists for each computer?

How do I determine if my computer is NTSC, PAL or SECAM?

For the Atari 1200XL and Atari 800XE, it is very simple, there is only one version.

The distinction between NTSC and PAL (or SECAM) is also quite easy to make, with a simple PEEK instruction in BASIC: PRINT PEEK(53268)

• If you get 15, your computer is NTSC
• If you get 1, your computer is PAL or SECAM

The difficulty comes with PAL or SECAM computers, because you have to look at the video sockets (monitor) on the back of the computer. Which one do you see?

• 5-pin 180° DIN? Then your Atari 800XL, 130XE or XEgs is PAL
• 6-pin 240° DIN? Then your Atari 800XL, 130XE or XEgs is SECAM

Special thanks to Jerome Delsarte for all his expertise on video signals.

Knowledge base article: kb-hardware-0003-atari-8bit-ntsc-pal-secam-peritel
REV. 007.