From Retro CDN
SCART (from Syndicat des Constructeurs d'Appareils Radiorécepteurs et Téléviseurs) is a French-originated standard and associated 21-pin connector for connecting audio and video equipment to television sets. Also called Péritel (especially in France, where the SCART word is not normally used) and Euroconnector. SCART makes it easy to connect VCRs, DVD players, set-top boxes (Pay TV, analog or digital cable, terrestrial digital TV), home computers, video game consoles and other equipment to television sets with optimal quality.
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 or through an American-originated RCA connector.
SCART attempts to make connecting video devices together much simpler, by providing one plug that contains all the necessary signals, 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 pretty high, around 1V, so the signals are effectively immune to noise.
SCART is bidirectional regarding standard composite video. A television set will typically send the antenna signal to the SCART sockets all the time and watch for a returned signal, to display it instead. This allows to have "transparent" set-top boxes, without any tuner, which just "hook" and process the television signal before it gets displayed.
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 signal 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 signal to the television set for viewing or simple recording control purposes. Alternatively, the VCR could use the signal from the television set, in which case it would be unadvisable to change channels on the television set during the recording.
The standard has been extended at the end of 1980s to support the new S-Video signals.
- SCART cannot carry both S-Video and RGB signals at the same time. It is however possible to output S-Video and RGB alternatively, for example from an S-VHS + DVD combo player, and the TV set will adapt automatically if it understands SCART's S-Video extension.
- SCART cannot carry component video (YPbPr) signals. The advantage of transmitting component rather than RGB is however questionable; the only clearly visible improvement in quality is when switching from composite/antenna to S-Video/RGB/component formats.
- SCART cannot transmit 5.1 or higher surround sound formats. But carrying a 5.1 signal to the TV set is of little interest, as such a signal is only usefully directed towards a surround sound system. In general, 5.1 sound is new to European TV; it only started to appear in 2004 on selected satellite channels.
- SCART cannot transmit a digital picture. The new (digital) audio+video HDMI connector is often referred to as 'Digital SCART'. From this, it appears that there will never be a second generation analog SCART to address the above limitations.
- Maximum SCART cable length is estimated to about 10 to 15 meters without relay.
Note that there are quality differences in SCART cables. While a proper SCART cable would use 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.
To non-destructively verify if a SCART cable uses coax cables, unscrew the strain relief at the SCART connector and fold open the plastic shell.
SCART Pin-out, (*) marking an extension to the original standard:
+------------------------------------------+ | 1 3 5 7 9 11 13 15 17 19 | 21 | \ | 2 4 6 8 10 12 14 16 18 20 \ +--------------------------------------------+
- AUDIO Output Right
- AUDIO Input Right
- AUDIO Output Left
- AUDIO Ground
- BLUE Ground
- AUDIO Input Left
- Function Switching
- GREEN Ground
- D²B Input
- D²B Output
- RED/(*)Chroma Ground
- D²B Ground
- VIDEO/Sync/(*)Luminance Ground
- Blanking Ground
- VIDEO/Sync/(*)Luminance Output
- VIDEO/Sync/(*)Luminance Input
- Common Ground (metal shield)
Pin 8 is a signal from the source that indicates the type of video present.
- 0V means no signal, or internal bypass
- +6V means a widescreen (16:9) signal(*)
- +12V means a normal (4:3) signal
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.