Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!samsung!munnari.oz.au!labtam!cnw01!iann From: iann@cnw01.storesys.coles.oz.au (Ian Nicholls) Newsgroups: comp.sys.amiga.datacomm Subject: Re: 19200bps Message-ID: <1252@cnw01.storesys.coles.oz.au> Date: 9 May 91 05:13:43 GMT References: <1991May5.185645.12902@cunixf.cc.columbia.edu> <1991May5.201708.452@cec1.wustl.edu> Organization: Coles Myer Ltd., Melbourne, Australia Lines: 29 In dillon@overload.Berkeley.CA.US (Matthew Dillon) writes: > A normal phone line has a bandwidth of around 38KBaud. As any > RF/electrical engineer will tell you, it's nearly impossible to utilize > all the available bandwidth of a medium. It's hard enough to utilize > half of it, which is what 9600bps (V.32) modems do now (9600bps full > duplex = 19.2KB bandwidth). The best you will ever see on a phone line > is probably around 19.2KB uncompressed. I thought that the higher speed modems used a different baud from bps. That is, a 2400 bps modem still sends at 1200 baud, it just sends two bits at a time (by phase-shifting; each state uses a different quarter-phase ). The 9600 buad modems use some sort of trellis encoding, so that sixteen states can exist, meaning four bits at a time get sent, but still at 2400 baud (states per second). From this basis, higher speeds can be possible with a more sensitive discriminator circuit, to detect more states. I don't know what the ultimate speed would be, but it won't be cheap. My reference is the Byte magazine, sometime in the past three years. You'll have to look up an index if you want the exact issue. -- "If it's OK to start by stealing pencils, where then do we draw the line?" Ian Nicholls Phone : +61 3 829 6088 Fax: +61 3 829 6886 \_o_/ Coles/Myer Ltd. E-mail: iann@cnw01.storesys.coles.oz.au \\| L1 M11, PO Box 480, Glen Iris 3146, Australia \\