Date: Fri, 20 Oct 2000 01:40:44 +0100 (BST) From: Andrew Gordon <arg@arg1.demon.co.uk> To: Hellmuth Michaelis <hm@hcs.de> Cc: freebsd-isdn@freebsd.org Subject: Re: ISDN S0 bus wiring configurations Message-ID: <Pine.BSF.4.21.0010181013480.20849-100000@server.arg.sj.co.uk> In-Reply-To: <20001018064726.A7EFD3E8@hcswork.hcs.de>
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On Wed, 18 Oct 2000, Hellmuth Michaelis wrote: > >From the keyboard of Andrew Gordon: > > > > > > I have put up a text about ISDN S0 bus wiring configurations at > > > > > > http://www.freebsd-support.de/i4b/isdn-cabling.txt > > > > > > Corrections and additions welcome! > > > > It seems odd that you mention only 75R and 150R cable impedance, when most > > people probably use 100R cable (and termination is specified as 100R). > > This is how it can be read in I.430. As far as i understand it, every type > of cable has to be terminated with 100 Ohms but the maximum length varies > with the cable impedance. I read it as saying that the correct cable impedance is 100 Ohms, but allowance has to be made for people using wrong or poorly-characterized cables. Actually, I.430 doesn't seem to make any statement about what the bus cabling should be - neither characteristic impedance nor velocity factor are specified, yet both are relevant. BT's wiring instructions specify that cable to specification CW1750 should be used (this is similar to cat-5). BT and several other sources say that EN50098-1 is the definitive specification for S-bus wiring, but unfortunately I do not have a copy. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isdn" in the body of the message
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