SCART
SCART or Scart is a European standard for plug connections in audio and video devices such as televisions and video recorders . Other names are Euro-AV , Euroconnector , Peritelevisions-Connection and, in France, Péritel . In the USA and Japan , SCART is not used and is only installed in export devices. The acronym SCART stands for French “ S yndicat des C onstructeurs d ' A ppareils R adiorécepteurs et T éléviseurs” (Association of manufacturers of radio receivers and televisions) . The properties of SCART are standardized in EN 50049-1.
AV-Link is an extension of this point-to-point connection to a bus, for example to connect TV sets, video recorders, satellite receivers with a continuous line .
operation area
The SCART connection tries to simplify and standardize the connection of different video devices, as it contains all the necessary signals in a single, multi-pin connector and forms a cross-manufacturer standard. The analog signal forms RGB , FBAS (also called composite video or CVBS , with YUV color coding for PAL or YIQ color coding for NTSC (outdated, today also YUV)) and - with newer devices - S-Video can be controlled via SCART With the same color coding as composite / FBAS, but in contrast to this, transmitted on two separate lines for Y and C (= UV or IQ). Some device manufacturers are now promoting a high-resolution, direct “YUV component video signal output” ( YPbPr is sometimes used instead of YUV , which is based on the same principle (color difference signals), but uses different coefficients and is therefore not compatible with YUV); this is not standardized for the SCART connection and is therefore currently still proprietary . A YUV output via the three RGB lines must be activated or selected in the device menu. Digital video and audio signals (see HDMI or digital YCbCr ) are not supported.
Mechanical construction
On the one hand, the asymmetrical design offers practical protection against polarity reversal (the plug cannot be inserted the wrong way round). On the other hand, its simple mechanical construction often causes interference in the signal path. Because of this, but also because of the lack of locking options against pulling out, SCART was never able to establish itself in the professional and broadcast sector. Instead, D-Sub connectors are used there for the switching signals and BNC connectors for AV signals . Some manufacturers of SCART connectors offer "luxury versions" in which, for example, the contacts in the carrier are encapsulated and / or gold-plated.
Differences in quality
Since analog signals are transmitted in the SCART cable, a bad cable can considerably reduce the picture quality compared to a good one; visible effects can occur, especially at lengths over 3 m.
Cables that are offered cheaply often have no internal coaxial cables and only a common (external) shield. Therefore, the sound is particularly disturbed by the adjacent unshielded video lines, which can be noticeable in certain picture content (e.g. text overlays) through a rattling noise.
A lack of shielding and unsuitable isolation (reflections) also affects the video signal, which can be noticeable as a lack of sharpness and washed-out colors. Likewise, if there is no or inadequate shielding, the sensitivity to high-frequency radiation is increased, so that there is picture or sound interference from strong transmitters in the vicinity (radio transmitters, amateur radio, etc.).
Without a suitable insulating material ( dielectric ) with a suitable wave impedance , cables with individual shielding are not much better. This is particularly noticeable with digital signal sources (for example DVD players or digital receivers ), as these provide a much better picture quality than, for example, a VHS video recorder.
development
From around 1976, televisions were equipped with what was then new, energy-saving switched - mode power supplies . This constructive measure enabled for the first time a cost-effective (compared to 50 Hz transformers in early television sets with mains separation) effective galvanic separation of the television chassis from the mains. It can therefore be at safe mass (earth) potential instead of 110 to 240 volts as it used to be. Peripheral devices such as VCRs, video disc player or video games have now been able without further expensive measures such as coupling transformers for electrical isolation or a UHF modulator safely be connected via small-signal connection to a TV. At the same time, the coaxial antenna connector was also connected directly to the tuner without coupling capacitors. In addition to low-loss transmission of the video signal, audio stereo signal transmission from the video recorder or video recorder to the television set was also possible for the first time .
On the international market, especially in Japan and the USA, there were many manufacturer-specific connections that often prevented devices from different manufacturers from being connected to one another. There were differences in the dimensions of the connectors as well as the electrical specifications of the signals. For this reason, the SCART standard was developed in Europe as early as 1978 - together with the plans for its own satellite television TV-SAT - in France . The first television sets with a SCART interface came onto the market in Germany and Austria in 1982. The direct forerunner of SCART was the six-pin DIN connector , which transmitted a composite video and a stereo audio signal, but only in one direction. Because of the still rare network separation in televisions, it was only moderately widespread. The most common connection in private television and video at that time (and remained so until the early 1990s) was the high-frequency connection via antenna cable, in which the AV signal was modulated onto a built-in UHF auxiliary transmitter. From the beginning of the 2000s, a connection between video / DVD / HD recorders is no longer possible due to a lack of free HF channels, which is why these have been completely replaced by SCART, component and HDMI connections. In America and Japan, however, SCART is almost unknown to this day.
The SCART connection was also a protectionist development: it was developed in France around 1978 to prevent imports of television sets from other countries. Originally there were laws in France that only allowed the import of television sets if the special black and white standard with 819 lines was supported. Since this was only used in France, manufacturers in other countries were forced to spend high development costs on supporting this standard, so there were almost no imported devices. However, when the 819-line standard was no longer used in France, there were no plausible reasons for this import restriction. From around 1981 onwards, all television sets offered in France had to have a SCART socket instead. Since this meant only a small additional effort for the manufacturer and the advantages were quickly recognized, it became the standard for inexpensive video recorders.
RGB video
The RGB signal in the SCART standard is inseparably linked to the plans for early satellite TV satellite TV connected early 1980s, the color information should not more per quadraturmoduliertem color carrier for PAL ( P Hare A lternating- L ine, rows of alternating Phase), but rather according to the MAC method ( M ultiplex- A nalogue- C omponents, analog components in time-division multiplex) in the SCART cable via separate RGB lines. It can also be seen as a relic of TV-SAT that the RGB lines in the SCART connector, in contrast to all others (except for the data lines), are unidirectional (an interactive television operation, i.e. that a television would have sent its picture back to TV-Sat was never planned).
After TV-SAT failed, many SCART cables came onto the market (and continue to do so to this day) in which not all pins are occupied, often only the FBAS and audio signals are transmitted. Fully assigned cables are often given the marketing designation “RGB cables” or “RGB video”. This is of particular interest for video game consoles, as it enables consoles that supply color information using a modulation method other than PAL ( e.g. NTSC ) to be connected to televisions. With DVD players and modern television receivers, the use of such a cable can lead to an improvement in the picture quality, since the transmission via FBAS inherently deteriorates the signal (modulated color carrier instead of individual lines).
Since no image synchronization impulses are sent on RGB lines 7 , 11 and 15 (except in the so-called " Sync-on-Green " mode, which can be activated on some devices), the receiver uses RGB mode for synchronization (i.e. with applied RGB switching voltage (pin 16)) of the additionally transmitted signal at the video input (pin 20). In most cases, not only the required sync pulses but also a full composite signal are transmitted there, so that devices that cannot accept RGB (especially video recorders) can work without any problems.
It is not possible to make RGB and S-Video available simultaneously, since the latter uses pin 15 for the transmission of the separate color signal ( chrominance ) for a purpose other than that intended . Some devices also transmit the chroma signal via pin 11. S-Video was not (yet) provided for in the original SCART standard, which is why the connector has too few poles to offer its own cable.
Pin assignment
| View of the socket from the outside or the solder side of the plug (pin 21 = outer shielding plate) |
| Pin code | meaning | description | |
|---|---|---|---|
| Audio | |||
| 1 | Audio output R | Typ. level 0.5 V eff @ R i <1 kOhm ≈ −4 dBm with 54% modulation of the sound carrier |
|
| 3 | Audio output L or mono | ||
| 2 | Audio input R | ||
| 6th | Audio input L or mono | ||
| 4th | Audio ground | ||
| RGB / YUV | YPbPr / S-Video | |||
| 7th | Input / output RGB – blue or YUV – V / Pb | Signal voltage max.0,7 V ss @ Z = 75 ohms | |
| 5 | Ground for pin 7 | ||
| 11 | Input / output RGB – green or YUV – Y | 0.7 V pp @ Z = 75 Ω | |
| 9 | Ground for pin 11 | ||
| 15th | Input / output RGB-red or YUV-U / Pr or S-video chrominance (C) | 0.7 V ss (color burst : 0V_ ± 0.15 V ss ) @ Z = 75 ohms | |
| 13 | Ground for pin 15 | ||
| Data / switching signals | |||
| 8th | TV / AV switching / aspect ratio ( switching voltage ) | Level 0 = 0..2 V - = TV (standard), Level 1A = 4.5..7 V - = AV (16: 9), Level 1B = 9.5..12 V - = AV (4: 3) @ R i > 10k ohms | |
| 10 | Data 1 (e.g. input D²B | (Serial multimedia bus ) or clock signal DDC -SCLK [Ser. Data bus according to I²C ]), (often unoccupied) | |
| 12 | Data 2 (e.g. output D²B | or data DDC -SDAT [Ser. Data bus according to I²C ]), (often unoccupied) | |
| 14th | Digital ground to pin 8 | 10 & 12, (IR input) | |
| 16 | originally blanking. ( Blank -) signal, the device also AV / RGB switch | 0..0.4 V - (low = FBAS), 1..3 V - (high = RGB) @ Z = 75 Ohm | |
| 18th | Ground for pin 16 | ||
| FBAS / FBAS decoder / S-Video luminance | |||
| 19th | Output composite video (sync) or cod. Baseband to the decoder or S-Video Luminance | Signal voltage & sync pulses 1 V ss @ Z = 75 Ohm | |
| 17th | Video ground for pin 19 & 20 | ||
| 20th | Input composite video (sync) or decod. FBAS video from decoder or S-video luminance | 1 V pp @ Z = 75 ohms | |
| Dimensions | |||
| 21st | Cable shield ( ground ) | ||
Wiring of SCART cables
Minimum wiring
| Fct | Pin code | screening results mung |
Pin code | signal |
|---|---|---|---|---|
| Audio Out R | 1 | E. | 2 | Audio In R |
| Audio out L | 3 | E. | 6th | Audio In L |
| Audio In R | 2 | E. | 1 | Audio Out R |
| Audio In L | 6th | E. | 3 | Audio out L |
| Audio ground | 4th | L. | 4th | Audio ground |
| AV switch. | 8th | E. | 8th | AV switching (aspect ratio) |
| FBAS mass | 17th | L. | 17th | FBAS mass |
| FBAS Out | 19th | E. | 20th | FBAS Video In |
| FBAS In | 20th | E. | 19th | FBAS video out |
| shielding | 21st | - | 21st | shielding |
Shielding:
- L: connection to the shield (conductive)
- E: single shield
This minimum circuit is only suitable for a composite video signal, but not for S-Video or RGB.
Full circuit
| Fct | Pin code | screening results mung |
Pin code | signal |
|---|---|---|---|---|
| Audio Out R | 1 | E. | 2 | Audio In R |
| Audio out L | 3 | E. | 6th | Audio In L |
| Audio In R | 2 | E. | 1 | Audio Out R |
| Audio In L | 6th | E. | 3 | Audio out L |
| Audio ground | 4th | L. | 4th | Audio ground |
| AV switch. | 8th | E. | 8th | AV switching (aspect ratio) |
| D²B In / CLK? | 10 | - | 10 | D²B In or clock (CLK) |
| D²B Out / DT? | 12 | - | 12 | D²B Out or Data (DT) |
| Digi. Dimensions | 14th | - | 14th | Digi. Dimensions |
| RGB-B / YUV-V | 7th | E. | 7th | RGB-B / YUV-V |
| RGB-B ground | 5 | L. | 5 | RGB-B ground |
| RGB-G ground | 9 | L. | 9 | RGB-G ground |
| RGB-G / YUV-Y | 11 | E. | 11 | RGB-G / YUV-Y |
| RGB-R ground | 13 | L. | 13 | RGB-R ground |
| RGB-R / YUV-U | 15th | E. | 15th | RGB-R / YUV-U |
| RGB-S blank | 16 | E. | 16 | RGB blank or RGB / FBAS toggle. |
| RGB-S ground | 18th | L. | 18th | RGB-S ground |
| FBAS mass | 17th | L. | 17th | FBAS mass |
| FBAS Out | 19th | E. | 20th | FBAS Video In |
| FBAS In | 20th | E. | 19th | FBAS video out |
| shielding | 21st | - | 21st | Cable shield |
- L: connection to the shield (conductive)
- E: single shield
disadvantage
The construction details resulting from the standard can lead to contact problems and damage when using the plug, especially if it is frequently plugged in:
- The individual contacts are flat and thin, and they are fixed inside the connector using small tongues. This can easily bend contacts or slide backwards in the carrier.
- The ground plate sometimes gets stuck in the socket when it is removed.
The standard does not require the sockets and plugs to be screwed onto the circuit board or the housing. Therefore, the easily breaking solder joints have to absorb forces that act on the plug and socket when they move. Due to the generally angled cable routing, a slight pull or pressure on the rather rigid cable is sufficient to lever the plug out of the socket on one side; The result is a picture or sound failure that cannot be clearly assigned to the SCART connection.
Norms and standards
- DIN EN 50049-1: 1998 Characteristic values for the small-signal connection between electronic devices for home use and similar applications: Peritelevison connection. German version of EN 50049-1: 1997 + A1: 1998. Published November 1998.
- DIN EN 50157-1: 1999-05 Characteristic values for the small signal connection between electronic devices for home use and similar applications: AV. link - Part 1: General; German version EN 50157-1: 1998
- DIN EN 50157-2-1: 1999-05 Characteristic values for the small signal connection between electronic devices for home use and similar applications: AV.link - Part 2-1: Qualitative adjustment of signals and automatic selection of signal sources; German version EN 50157-2-1: 1998
- DIN EN 50157-2-2: 1999-05 Characteristic values for the small signal connection between electronic devices for home use and similar applications: AV.link - Part 2-2: Basic system-oriented commands; German version EN 50157-2-2: 1998
- DIN EN 50157-2-3: 1999-05 Characteristic values for the small signal connection between electronic devices for home use and similar applications: AV.link - Part 2-3: System-oriented application; German version EN 50157-2-3: 1998
Successor systems
- Golden SCART , further development for high-resolution HD-MAC signal
- High Definition Multimedia Interface (HDMI), current standard
literature
- Carsten Meyer: French Connection. Scart pitfalls: Connect DVD player, video recorder and AV receiver correctly. In: c't 12/2003. Pp. 210-213. This article gives a brief, critical overview of SCART and gives tips on using SCART. Also available online in the c't archive (for a fee).
Web links
- SCART pinout (English)