Editing SCART (section)

== Design ==

=== Cables ===
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 are: pins 1 and 2, pins 3 and 6, pins 17 and 18, pins 19 and 20.

The original SCART specification provided for different cable (cordset) types denoted by a key color, but color-coding is rarely used and cables often use different, non-standard configurations.

{| class="wikitable"
|-
! colspan="2" | Type
! Ring color
! Pins
! Description
! Symmetric
|-
| '''U'''
| Universal
| black
| 1–20, 21
| Fully wired cable.
| no
|-
| '''V'''
| Video only
| white
| 17–20, 21
| Only composite wires.
| yes
|-
| '''C'''
| Combined
| grey
| 1–4, 6, 17–20, 21
| Composite Video and Audio
| yes
|-
| '''A'''
| Audio only
| yellow
| 1–4, 6, 21
| Audio
| yes
|-
| '''B'''
| Bus
| green
| 10, 12, 21
| Only data connections
| Depends on protocol used
|}

Maximum SCART cable length is estimated to be about 10 to 15 metres without amplification.{{Citation needed|date=January 2009}}

Due to the relatively high signal voltages 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.{{Citation needed|date=January 2009}} Also, since many TVs are [[appliance classes|Class II]] (double-insulated) rather than earthed, the large exposed shield on the SCART connector will be held at approximately half mains voltage if it is plugged into a powered TV with the other end unplugged. If the cable is then plugged into an earthed device with a metal case, inadvertent contact with the SCART cable shield while the earthed device is touched with the other hand can cause a painful electric shock. For this reason the device end of the cable should always be plugged in first and the TV end plugged in last.<ref>{{cite web|url=http://www.diynot.com/forums/viewtopic.php?t=11972 |title=Electric shock off aerial coax |date=7 August 2004 |publisher=DIYnot.com |access-date=2012-06-15}}</ref><ref>{{cite web|url=http://www.dtg.org.uk/dtg/press_releases/dtg_napit_201110.pdf|title=Guide to preventing shocks from entertainment systems|work=Digital TV Group|url-status=dead|archive-url=https://web.archive.org/web/20160306172331/http://dtg.org.uk/dtg/press_releases/dtg_napit_201110.pdf|archive-date=March 6, 2016|access-date=15 June 2012}}</ref><ref>{{cite web|url=http://www.chatzones.co.uk/cgi-bin/discus/show.cgi?tpc=5557&post=15775#POST15775|title=:: EPE Chat Zone :: Radio Bygones Message Board ::: SCART Shock|publisher=Chatzones.co.uk|url-status=dead|archive-url=https://web.archive.org/web/20160416195814/http://www.chatzones.co.uk/cgi-bin/discus/show.cgi?tpc=5557&post=15775|archive-date=April 16, 2016|access-date=2012-06-15}}</ref>

Quality differences exist in SCART cables. While a proper SCART cable uses miniature [[coaxial cable]]s 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 on a cheap SCART cable is that a TV outputs a composite video signal from its internal tuner and this is induced or [[crosstalk]]ed onto an incoming video signal due to inadequate or non-existent screening; the result is ghostly images or shimmering superimposed on the incoming signal. To non-destructively verify if a SCART cable uses coaxial cables, unscrew the [[strain relief]] at the SCART connector and fold open the plastic shell.

Using higher-quality cables such as those with ribbon cords that have properly shielded coaxial cables inside might help in reducing a 'ghosting' effect, but it does not always eliminate it due to various factors. A more permanent method is to remove pin 19 (Video Out) from the SCART plug that is put into the TV, preventing a signal from being broadcast by the TV into the cable, so it cannot cross-talk with the incoming signal.

=== Blanking and switching ===

Two pins provide switching signals.

Pin 8, the ''switch signal'' pin, carries a DC voltage 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 aspect ratio|16:9]]) signal
*9.5 V–12 V (nominal 12 V) means a normal ([[Fullscreen (aspect ratio)|4:3]]) signal

Pin 16, the ''blanking signal'' 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 a high frequency (up to 3&nbsp;MHz) signal that blanked the composite video.  The RGB inputs were always active and the signal 'punches holes' in the composite video. This could be used 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 auto-detect the presence of the S-Video signal but more commonly the S-Video input needs to be manually selected. The same for the rare component YPbPr, which is in many cases implemented over a composite or RGB SCART.

=== Non-standard extensions ===
[[File:SCART gold plate peritel.jpg|thumb|RGB-capable SCART ([[gold plated]])]]
[[File:Fake-scart-brkn.jpg|thumb|Non-RGB SCART male connector. Only 10 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 connector or socket that actually have 10 wires connected and are thus not RGB / S-Video capable, but only [[CVBS]].]]

The use of the data pins was not standardised in the original SCART specification, resulting in the use of several different protocols, both proprietary protocols and semi-proprietary protocols based on standards such as [[D²B]].

Some of the most creative usages appeared in analogue satellite receivers. The function of decoding hybrid, time-compressed analogue-digital MAC transmissions into RGB and analogue audio was akin to making a digital receiver out of an analogue one. The D²B pins (10 and 12) were used for communicating with [[satellite dish]] positioners and for driving magnetic [[polarizer|polarisers]], before these became incorporated into [[Low-noise block converter|LNB]]s. The daisy-chaining features were used to connect both a Pay TV decoder and a dish positioner/polariser to a single ''Decoder'' socket on the receiver.<ref>Based on a [[Pace Micro Technology]] Prima analogue receiver manual and a DATCOM AP-500/AP-700 dish positioner manual.</ref>

CENELEC EN 50157-1 introduced [[AV.link]] as a standardised protocol to carry advanced control information between devices. It is a single-wire serial data [[Bus (computing)|bus]] and allows carrying remote control information and to negotiate analogue signal types (e.g. RGB). AV.link is also known as nexTViewLink or trade names such as SmartLink, Q-Link or EasyLink. It appears as the [[Consumer Electronics Control]] channel in HDMI.

The data pins, 10, 12, 14, were used by some manufacturers for [[Dolby Pro Logic]], surround and multichannel on their TV sets (some high end models with built in Dolby decoders, and external surround speakers, both CRT, LCD and  plasma sets, and only in Europe - and European versions of Japanese TV Sets and DVD players -, and mainly on S/PDIF), in order to connect a DVD player to the TV set and stream the Dolby and DTS to the surround of the TV set {{Citation needed|date=April 2023}}. However, this protocol was rarely used, as it was limited only to a certain manufacturer, and the connections were different from a manufacturer to another, and in some cases, it was only commanded by the pin 8. In this case, it was unusable with RCA to SCART adapters. Also, if a Compatible TV with such connection and a compatible DVD with such connection, but from different manufacturers were interconnected, the surround might not work, and only the stereo sound from the DVD player was available to the TV, because some manufacturers did not use SPDIF, but an own protocol. Also, this connection might be also lost, if the connection of the DVD with the TV was made indirectly (through a VCR in daisy chaining mode, for example), however, some VCR allowed the pass-through of these signals. Some DVD player manufacturers on some models offered SPDIF only on SCART, and an adapter in order to extract the digital audio signal to send it to a home cinema. To the present day this connection remains rare, as HDMI, S/PDIF, and TOSLINK can provide multichannel audio, also some TV sets with Surround built in may have an Optical or S/PDIF INPUT, beside Output {{Citation needed|date=April 2023}}.