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Xref: sserve comp.os.linux.misc:29993 comp.os.386bsd.misc:4128 sci.electronics:84386 Newsgroups: comp.os.linux.misc,comp.os.386bsd.misc,sci.electronics Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!msuinfo!caen!zip.eecs.umich.edu!newshost.marcam.com!news.mathworks.com!uhog.mit.edu!news.mtholyoke.edu!nntp.et.byu.edu!news.provo.novell.com!ga!kevin From: kevin@novell.com (Kevin White) Subject: Re: 16550 detection Message-ID: <1994Nov18.210403.29940@novell.com> Sender: news@novell.com (News Administrator) Nntp-Posting-Host: na Organization: Novell Inc., San Jose, Califonia References: <3a8u29$mi@awfulhak.demon.co.uk> <CzF7qx.9yH@indirect.com> <1994Nov18.082900.12223@slate.mines.colorado.edu> Date: Fri, 18 Nov 1994 21:04:03 GMT Lines: 45 In article <1994Nov18.082900.12223@slate.mines.colorado.edu> mbarkah@slate.mines.colorado.edu (Ade Barkah) writes: >Barnacle Wes (wes@indirect.com) wrote: >: Brian Somers (brian@awfulhak.demon.co.uk) wrote: >: : Please inform someone who thought that bps was the same as baud of >: : their ignorance.... > >: In the days of 2400 bps/Baud modems, they were. A 2400 bps modem >: transmits and receives (transcieves? ;^) two tones, one means "0" >: and the other "1". If you use *more tones*, you can encode more than >: one bit in each state change. > >Actually, I don't even think for 2400 bps modem 1 baud==1 bps. >If I remember, the 2400 bps modems already use quadrature >amplitute modulation (qam) encoding, with 600 baud/s at 4 bits >per baud. > >: The Trailblazer used 512 different tones, and a unique encoding >: method called (if I remember correctly) trellis encoding, and 7 >: state changes/sec, or Baud, to achieve ~20,000 bps throughput. > >I'm not familiar with Trailblazers (I'm assuming you're talking >about PEP) but 7 baud/s seems pretty slow. Maybe you ment it >the other way: the trellis encoding gives it 7 (or 8) bits >per baud, running at 512 bauds/sec. This is still far short >of 20 kbps. A more likely scenario would be 8 bits per baud >at 2400 baud per second for a 19,200 bps throughput (or >16.8 kbps if using 7 bits per baud). > >-Ade Barkah >-- >Renaissance Knowledge Systems, Englewood, Colorado. It was not Trellis encoding but he is correct that the Telebit protocol ran at about 7 Baud with up to 512 channels each with up to 6 bits per baud. Giving a maximum of about 18,000 bps. Telebit now has variations on the theme that are better for interactive use (20 Baud). It is reported to be one of the best modems for dealing with noisy channels. It adapts to line conditions to only use as many channels and as many bits per channel as the line can handle. Each channel is a separate frequency. An FFT is peformed to separate the different frequencies and I believe they are then each encoded using conventional quadrature amplitude modulation. Kevin white