Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!dali.cs.montana.edu!caen!zaphod.mps.ohio-state.edu!wuarchive!uunet!mcsun!ukc!stl!ajdh From: ajdh@stl.stc.co.uk (Andrew J D Hurley) Newsgroups: comp.sys.acorn Subject: Re: BBC Microcomputer Message-ID: <4458@stl.stc.co.uk> Date: 22 May 91 14:30:24 GMT References: <2784@lee.SEAS.UCLA.EDU> <1991May20.034649.1@vax1.tcd.ie> Sender: news@stl.stc.co.uk Reply-To: "Andrew J D Hurley" Organization: BNR Europe Limited, London Road, Harlow, Essex, UK Lines: 35 In the referenced article hughesmp@vax1.tcd.ie writes: >In article <2784@lee.SEAS.UCLA.EDU>, cccph@jessica.cs.ucla.edu (Charles Hobbs) writes: >> >> The machine has been modified >> for 120 VAC, but not for NTSC (some screen lines go off the top of >> the screen, and I can't get any color, just shades of gray). > >The grey (if I remember correctly) is adjustable using a link... This is true, however, the composite video output is tuned to PAL, not NTSC. Unless the machine has also been modified for NTSC the colour encoding will be for PAL. If my understanding of PAL vs NTSC is correct the upshot of all this is that a colour PAL signal will come out as a mono picture on an NTSC set or perhaps worse - ie completely wrong colours due to completely different techniques of colour coding. PAL codes colour by luminance (mono picture) and chrominance (a combination of -blue and -red signals) the combination of which allows the calculation of red, green and blue. I beleive NTSC is rather different and for all I know the carrier frequencies are also different. Maybe someone makes a simple converter to produce NTSC coded PAL frequency signals from PAL ?? You are almost certainly better off trying to get an RGB to NTSC converter which will plug into the BBCs RGB port so avoiding problems with PAL colour coding. -- Andrew J D Hurley, ( ajdh@stl.stc.co.uk ) Mail route: uunet!ukc!stl!ajdh | Phone: +44 279 429531 x. 2535 BNR Europe Ltd., London Road, Harlow, Essex CM17 9NA, UK.