Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site watdcsu.UUCP Path: utzoo!watmath!watdcsu!herbie From: herbie@watdcsu.UUCP (Herb Chong [DCS]) Newsgroups: net.audio Subject: Re: CD Reflections - 44.1k? Message-ID: <854@watdcsu.UUCP> Date: Mon, 21-Jan-85 10:18:13 EST Article-I.D.: watdcsu.854 Posted: Mon Jan 21 10:18:13 1985 Date-Received: Tue, 22-Jan-85 04:58:14 EST References: <15100001@hpfcmp.UUCP> <3411@mit-eddie.UUCP> <1420@hplabs.UUCP> <755@clyde.UUCP> <258@petrus.UUCP> <272@mtxinu.UUCP> Reply-To: herbie@watdcsu.UUCP (Herb Chong [DCS]) Organization: U of Waterloo, Ontario Lines: 53 Summary: In article <272@mtxinu.UUCP> ed@mtxinu.UUCP (Ed Gould) writes: >When I studied signal theory briefly about 12 years ago, there was >a theorem stating that it was *impossible* to push more information >through a signal than the bandwidth of the signal, e.g., one can't >send more than k bits per second through a k Hz bandlimnited channel. This is almost true; your memory isn't quite right. There is also the different signal levels to consider. Suppose I were to agree decide that the S/N of the channel was sufficiently high to use a 4-level encoding of the data being transmitted (2 bits in one pulse). The pulses are distinguished by which one of the 4 levels is received. Thus, I'm transmitting 2*n bits/s in a channel bandlimited to n bits/s. This is equivalent to saying I'm transmitting 2*n baud. 1 baud != 1 bit/s in general. >Telephone voice-grade channels are 2700 Hz limited, filtering to allow >signals only from 300 Hz to 3000 Hz. So how do 4800 and 9600 bps >modems work over dialup circuits? (The telco carriers, by the way, >are strict about bandlimiting their signals, since they frequency- >multiplex them onto higher-bandwidth channels.) They don't transmit at 9600 bps, they transmit at 9600 baud. See above. >The answer seems to be that the theory that generated that theorem >wasn't completely correct. Maybe the Nyquist theorem shouldn't be >regarded as gospel, either. I'm afraid Nyquist knew what he was talking about. Theoretically, in a completely noise-free channel, it is possible to transmit all the information known to Man in a single pulse of a specified amplitude within any non-zero bandwidth. When there is noise, there is a limit to the information transfer rate. >-- >Ed Gould mt Xinu, 739 Allston Way, Berkeley, CA 94710 USA >{ucbvax,decvax}!mtxinu!ed +1 415 644 0146 Your's for enlightenment, Herb Chong, BASc Computer Consultant I'm user-friendly -- I don't byte, I nybble.... UUCP: {decvax|utzoo|ihnp4|allegra|clyde}!watmath!water!watdcsu!herbie CSNET: herbie%watdcsu@waterloo.csnet ARPA: herbie%watdcsu%waterloo.csnet@csnet-relay.arpa NETNORTH, BITNET, EARN: herbie@watdcs, herbie@watdcsu POST: Department of Computing Services University of Waterloo N2L 3G1 (519)885-1211 x3524