SCART

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SCART
A male SCART connector (21-pin)
Type	Analogue audio and video connector
Production history
Designer	CENELEC
Designed	1970s
Superseded	RCA, DIN (in Europe)
Specifications
Audio signal	Bi-directional Stereo
Video signal	Composite (bi-directional), RGB (uni-directional) or S-Video (sometimes bi-directional)
Data signal	D²B and widescreen switching
Pins	21 (21 wires:RGB / 10 wires:non-RGB) 10 (10 wires:non-RGB)
Pin out
Female connector seen from the front
Pin 1		Audio output (right)
Pin 2		Audio input (right)
Pin 3		Audio output (left)
Pin 4		Audio ground
Pin 5		Blue ground/Chroma input ground
Pin 6		Audio input (left)
Pin 7		Blue/Chroma input
Pin 8		Widescreen function switching
Pin 9		Green ground
Pin 10		D²B input
Pin 11		Green
Pin 12		D²B output
Pin 13		Red ground/Chroma ground
Pin 14		D²B ground
Pin 15		Red/Chroma
Pin 16		Fast switching
Pin 17		Composite video output ground/Sync output ground/ Luminance output ground
Pin 18		Composite video input ground/Sync input ground/ Fast switching ground/Luminance input ground
Pin 19		Composite video output/Sync output/ Luminance output
Pin 20		Composite video input/Sync input/ Luminance input
Pin 21		Common ground
Extensions to the original standard are in italics. D²B ("Digital Data Bus") is an IEC standard for a serial communication bus. It is a multi-master bus for home automation, and was originally developed by Philips in the 1970s.

SCART (from Syndicat des Constructeurs d'Appareils Radiorécepteurs et Téléviseurs) is a French-originated standard and associated 21-pin connector for connecting audio-visual equipment together. It is also known as Péritel (especially in France, where the SCART word is not normally used), 21-pin EuroSCART (Sharp's marketing term for an attempt to market the connector in the Asian region) and Euroconnector. ^[1]

The SCART connector first appeared on television sets in 1977. It became compulsory on all new television sets sold in France starting from January 1980. ^[2][3]

SCART makes it easy to connect AV equipment (including TVs, VCRs, DVD players and game consoles). In essence, it gathers together various common analog signal types into a single connector. Previously, each of these would have had their own socket, requiring numerous separate connections (and a "spaghetti" type mass of leads). The signals carried by SCART include both composite and RGB (with composite synchronisation) video, and stereo audio input/output. The standard was extended at the end of the 1980s to support the new S-Video signals. In addition, a TV can be awakened from standby mode or switched to video mode through a SCART connector.

In Europe, SCART is the most common method of connecting audio-visual equipment together, and has become the standard connector for such devices (even more so than the phono plug).^{[citation needed]} It is far less common elsewhere in the world.^{[citation needed]}

The official standard for SCART is CENELEC document number EN 50049-1.

SCART is sometimes referred as the IEC 933-1 standard.

[edit] Motivations and applications for SCART

Before SCART came, consumer TV sets did not offer a standardized way of inputting signals other than RF antenna ones, and even antenna connectors differed between countries. Assuming other connectors even existed, devices made by different companies could have different and incompatible standards. For example, a VHS VCR could output a composite video signal through a German-originated DIN-style connector, an American-originated RCA connector, or a BNC connector.

SCART sockets, common side (female connectors)

SCART attempts to make connecting video devices together much simpler, by providing one plug that contains all the necessary signals (refer to the Pinout to the right for details), and is standard across different manufacturers. SCART makes connecting such devices very simple, because one cable can connect any two SCART-compatible devices, and the connector is designed so that you cannot insert it incorrectly. Devices with multiple SCART connectors can pass the signals unchanged when not active, which allows daisy chaining of multiple signal sources into a single TV socket. The voltage levels are quite high, around 1V, so the signals have good noise immunity.

SCART is bi-directional regarding standard composite video and analog audio. A television set will typically send the antenna audio and video signals to the SCART sockets all the time and watch for returned signals, to display and reproduce them instead. This allows "transparent" set-top boxes, without any tuner, which just "hook" and pre-process the television signals.

This feature is used for analog Pay TV like Canal Plus and was in the past used for decoding teletext. A VCR will typically have 2 SCART sockets, one connecting to the television set, and another one for the set-top box. When idle or powered off, the VCR will forward the signals from the television set to the set-top decoder and send the processed result back to the television set. When a scrambled show is recorded, the VCR will drive the set-top box from its own tuner and send the unscrambled signals to the television set for viewing or simple recording control purposes. Alternatively, the VCR could use the signals from the television set, in which case it would be inadvisable to change channels on the television set during the recording.

SCART also enables a device to command the television set to very quickly switch between signals, in order to create overlays in the image. In order to implement captioning or subtitles, a SCART set-top box does not have to process and send back a complete new video signal, which would require full decoding and re-encoding of the color information, a signal-degrading and costly process, especially given the presence of different standards in Europe. The box can instead ask the television set to stop displaying the normal signal and display a signal it generates internally for selected image areas, with pixel-level granularity. This can be driven by the use of a "transparent" color in a teletext page.

SCART allows a connected device to power on and power off a television set, more precisely: to bring it in and out of standby mode, in the same way as a remote control would do. A VCR will optimally power on when a cassette is inserted, power on the television set (or switch it to video mode) and then start playing immediately if the cassette's write protection tab is absent. When turned off, the VCR will ask the television set to power off as well, which the set will do if it was powered on by the VCR's request and if it remained in video mode all along. Only some TV sets will do this - most only implement automatic switching to and from the SCART input.

[edit] Criticisms

Non-RGB 10-pin SCART male connector (coax AV cable). Only pins 2/6/7/8/11/15/16/17/18/20 are available. Some cheap cables or devices (DVD players, TVs) have a 21-pin SCART male/female connector or socket that actually have 10 wires connected and though are not RGB capable ("fake RGB"), but only CVBS.

Multi-AV SCART adaptors with Input/Output signal switch (gold & nickel). A common misbelief among game console owners is such connectors will allow RGB quality, while they are only CVBS and S-Video compliant.

• SCART cannot carry both S-Video and RGB signals at the same time. It is, however, possible to output S-Video and RGB alternately, (for example, from an S-VHS + DVD combo player), and the TV set will adapt automatically if it understands SCART's S-Video extension. Many DVD players sold in Europe offer the ability to output either RGB or S-Video, which is either selected in the DVD player's set-up menu or by a switch on the back of the system.
• RGB connections are not bidirectional. Bidirectional S-Video was added in an extension, although few devices support this, so downstream connections are almost always composite.
• SCART can sometimes be confusing for consumers. Most TV sets that have multiple SCART connectors have only one capable of receiving RGB and the other one capable of receiving S-video. Also, not all SCART cables make use of all the pins, often leaving out RGB signals. In many cases there is also no way to see which type of signal that is currently displayed on the TV set.
• SCART cannot officially carry non-RGB (e.g. YPbPr) component video signals, which are gaining ground as an improvement over S-Video in markets where SCART is not used. However, some manufacturers of set-top-boxes and DVD players are known to provide optional (menu-selectable), non-standard YPbPr output through the pins that are officially reserved for RGB color components.
• SCART is not designed to transmit digital video or audio signals. The new (digital) audio+video HDMI connector is often referred to as "digital SCART"^{[citation needed]}. From this it appears that there will never be a second generation analog SCART to address the above limitations.
• SCART is limited to two audio channels, meaning it cannot deliver surround sound with discrete surround channels, such as Dolby Digital or DTS.
• SCART connects are non-locking and are prone to falling off or getting loose, especially since the thick 21-wire cable is relatively heavy and often leaves the connector at a sideways angle. Loss of audio or video connection due to a loose SCART connector is relatively common. To allow limited locking, some connectors (such as the one portrayed on this page) have detents on the sides.
• The thickness and inflexibility of the cables, combined with the fact that they are connected to the plugs at an angle, can sometimes make it difficult to connect items of equipment, especially in confined spaces. Attempts at thinner or flat cables are more susceptible to cross-talk, or are unable to support all communication modes.
• The connector design requires the plug to be perfectly aligned over the socket before it can be inserted at all, whereas more recent connector designs are self-correcting if the plug is inserted at slightly the wrong angle.
• Cheap 10-pin SCART connectors can be very fragile and prone to breaking or losing pins, since they are big and hollow. 21-pin connectors are generally stronger.
• SCART connectors are large and cumbersome compared to most modern connectors (e.g. VGA) used in computers and the cabling is often bulky and heavy.
• Some of the SCART switching features are often poorly implemented although this is often more due to deficencies in individual equipment design than any inherent flaws in the SCART standard

[edit] Practical advice

Nearly all DVD players with SCART sockets output RGB video, which offers far superior picture quality to typical composite signals. However, many players do not have RGB output turned on by default but CVBS - this often has to be set manually in the player's setup menu or via switches on the back of the player.

High quality gold plated Péritel/SCART RGB AV coaxial cable for PlayStation 2.

The Nintendo GameCube, Nintendo Wii, Sony PlayStation 2, Microsoft Xbox and Microsoft Xbox 360 can output RGB, YCrCb, S-Video, or composite video. These consoles come with the standard composite video connector, but the manufacturers and third parties sell connectors for component video hookup and for RGB SCART hookup. Where the GameCube and Xbox automatically switch to the proper mode, the PlayStation 2 must be told via a selection in the system menu whether it is to use YPbPr or RGB component video. Also, some versions of legacy consoles such as Nintendo's SNES and Nintendo 64 (some, modified NTSC models only) are capable of outputting RGB signals (using the same cable as the GameCube).

Many older home computers (Amstrad CPC, later ZX Spectrum models, Commodore Amiga, Atari ST, BBC Micro and Acorn Archimedes, etc.) output RGB with composite sync suitable for SCART use, but most used varying non-standard DIN plugs. Standard-resolution arcade monitors use RGB signals with a composite sync, which is SCART-compatible.

Maximum SCART cable length is estimated to be about 10 to 15 meters without relay.

Due to the relatively high voltage used in SCART, "hot plugging" (connecting or disconnecting devices while they are on) is not recommended. Although there is no risk of personal injury, there is the possibility of damaging electronics within the devices if the connector is inserted improperly.

Quality differences exist in SCART cables. While a proper SCART cable uses miniature coax cables for the video signals, cheap SCART cables often use plain wires for all signals, resulting in a loss of image quality and greatly reducing the maximum cable length. A common problem is that a TV outputs a composite video signal from its internal tuner, and this is induced or cross-talked onto an incoming video signal due to inadequate or non-existent screening on a cheap SCART cable; the result is ghostly images or shimmering superimposed on the incoming signal. To non-destructively verify if a SCART cable uses coax cables, one can unscrew the strain relief at the SCART connector and fold open the plastic shell.

Although using higher-quality cables might help in reducing a 'ghosting' effect, a more permanent method is to remove pin 19 from the SCART plug that is put into the TV. Pin 19 is Video Out, and removing it prevents a signal from being broadcast by the TV into the cable in the first place, so it cannot cross-talk with the incoming signal. Cheaper SCART plugs can sometimes have the pins pushed inside the connector housing so as to remove it in a non-destructive manner (and thus allowing for its replacement in the future should the need arise by simply unscrewing the housing and pushing the pin back through its hole), though sometimes the pins are fixed in place on the inside by glue or rubber and can only be removed by forcefully twisting them off entirely. Generally though, for a standalone TV there is no need for video output on the TV end of the SCART plug, so in the majority of cases removing it completely should not be a problem. Whichever way it is done, however, once it is the SCART is rendered incapable of transmitting a video signal from that end of the cable, so it would be wise to mark it as such for future reference.

Gold-plated SCART connectors, which do not corrode and deliver a cleaner signal, might be preferable, although they always cost more than nickel ones. However, gold-plated connectors only give better performance when both plug and socket are gold plated. Gold and nickel are galvanically very different metals, and although inserting a gold-plated plug into a nickel plated socket may make a small difference at first, any atmospheric moisture that is present near the connector will cause an electrolytic reaction between the dissimilar metals. This will result in the nickel-plated connector corroding much more rapidly than it would if both connectors were nickel-plated. For good long-term connection quality it is always better to use matching connector materials.

[edit] Blanking and switching

Two pins provide switching signals.

Pin 8, the function switching pin, carries a low frequency (less than 50 Hz) signal from the source that indicates the type of video present.

0 V-2 V means no signal, or internal bypass

4.5 V-7 V (nominal 6 V) means a widescreen (16:9) signal

9.5 V-12 V (nominal 12 V) means a normal (4:3) signal

Pin 16, the fast switching pin, carries a signal from the source that indicates that the signal is either RGB or composite.

0 V-0.4 V means composite.

1 V-3 V (nominal 1 V) means RGB only.

The original specification defined pin 16 as fast blanking, a high frequency (up to 3 MHz) signal that blanked the composite video. The RGB inputs were always active and the fast blanking signal 'punches holes' in the composite video. The SCART connector uses this to overlay subtitles from an external Teletext decoder.

0 V-0.4 V means composite with a transparent RGB overlay.

1 V-3 V (nominal 1 V) RGB only.

There is no switching signal to indicate S-Video. Some TVs can autodetect the presence of the S-Video signal but more commonly the S-Video input needs to be manually selected.

[edit] Cables

An extension cable consists of a male plug at one end and a female socket at the other. In an extension cable all the wires within the cable connect to the identical pin number at each end.

The cables for connecting equipment together have a male plug at each end. Some of the wires such as ground, data, switching and RGB connect to the identical pin number at each end. Others such as audio and video are swapped so that an output signal at one end of the cable connects to an input signal at the other end. The complete list of wires that are swapped is: pins 1 and 2, pins 3 and 6, pins 17 and 18, pins 19 and 20.

Scart leads are available to buy in a wide range of stores fairly cheaply.

[edit] References

1. ^ Conector SCART (Euroconector). uvigo.es.
2. ^ La télé des années 80. croque-vacances.com.
3. ^ Le TI-99/4A et la Presse Informatique. perso.orange.fr/fabrice.montupet.

[edit] See also

• HDMI
• RCA jack
• RF connector

[edit] External links

• SCART connector pinout and cables schemes

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SCART