A sync separator circuit can be inserted directly into a SCART plug and the voltage needed to power the circuit is drawn directly from the console and works without any problems. This removes the composite video signal and leaves a clean composite sync signal. The composite video aspect of the video signal can be removed using a special circuit called a sync separator, sync cleaner or sync stripper as seen in figure 3. For consoles which only output sync over composite video, there is a solution. Consoles which can output composite sync include the Sega Mega Drive / Genesis 1 & 2, Super Nintendo (NTSC), Neo Geo AES, Atari Jaguar, Sega Saturn (JAPANESE model) etc. Unfortunately the most commonly used format in the world of retro gaming after-market cables is the sync over composite video RGB SCART cable, including those cheap arse cables of eBay (oops). These two problems can occur with the Super Nintendo, NTSC version, but can be cured using a composite sync RGB SCART cable, YAY! Problems includes screen drop-offs resulting in a blank screen during game play and also another effect called dot crawl. Another problem often experienced with sync over composite video RGB SCART cables are sync issues when connecting consoles to video up scalers like the Framemeister XRGB mini. Luckily both Mega Drive / Genesis consoles output composite sync as well as composite video, therefore, you just need an RGB SCART wired to support composite sync, and bingo! No more jail bars. This effect is legendary on the Sega Mega Drive / Genesis model 1 & model 2 when using a “sync over composite video” RGB SCART cable, however not exclusively reserved to those Sega consoles. This is due to the amount of channels occupying one wire and in the case of composite video this totals five (red, green, blue, VSYNC & HSYNC) as seen in figure 1, so cross-over interference is a common problem. Boosted sync is the practice of adding an inline amplifier to boost the sync signal, which is something that we have never done or advocated, as this may damage your video monitor or up-scaler.Ī composite sync RGB SCART cable can reduce a video effect often referred to as jail bars, which are faint on-screen horizontal lines displayed throughout game play and are more noticeable on patches of solid colours, and when using a modern flat screen television in-conjunction with a sync over composite video RGB SCART. Composite sync is also sometimes referred to as "pure sync", “clean sync” or "CSYNC". A composite sync or CSYNC RGB SCART supplies a clean timing signal without composite video interlaced on the same wire, as seen in figure 2 which gives a clearer picture in some cases. Therefore the "composite video" option is both the CSYNC signal (for RGB timing) and actual composite video (CVBS) both mashed together down the same wire (SCART pin 20). This is in-case the television doesn't support an RGB signal, therefore, you will still get a picture via composite video, be it a poorer image compared to RGB. “sync or CSYNC over composite video”, see figure 1. In terms of an RGB SCART the composite video signal is a mixture of sync as described above (which helps construct the RGB screen image) and composite video (CVBS), i.e. Sync is a timing signal made up from the horizontal sync (HSYNC) and vertical sync (VSYNC) which tells the television when to correctly display the image. An RGB SCART cable transmits on four separate wires (Red - pin 15, green - pin 11, blue - pin 7 & sync - pin 20), which gives it a cleaner picture, as opposed to a phono composite video cable which only uses one wire to handle all the picture data.
But a phono composite video cable is not the same video format as an RGB SCART cable. When referring to RGB SCART cables the term composite video can be confused with the more commonly used composite video format (CVBS) which normally uses a cable with two phono plugs (yellow and white) or three phono plugs (yellow, white and red), also known as RCA or Cinch cable. In both cases this can still be an RGB SCART cable.
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