Hmmm, that's interesting. So the 56Kbps limit is only because ISDN defines the channel to like that (whatever the official name for a channel in ISDN). So according to your explanation, the 56Kbps doesn't refer to the modem's ability to modulate bits onto the voice band at all. Why don't they just call it a 33.2Kbps modem, if that is what it's actually doing?
Fred -------------------------------------------------------------------------- Fred Ma Department of Electronics Carleton University, Mackenzie Building 1125 Colonel By Drive Ottawa, Ontario Canada K1S 5B6 [EMAIL PROTECTED] ========================================================================== > Date: Mon, 11 Feb 2002 12:07:49 +1100 > From: Chris Jaecker <[EMAIL PROTECTED]> > Subject: Re: TightVNC 1.2.2, is it beneficial? > > Fred, > > Just a quick clarification here:- 56k modems do not operate at 56Kbps, at > least not bi-directionally. Modems in general convert digital information > (bits) into analog (electrical representations of sound), and back. > Operating properly, a 56K modem converts the bits from your computer into > analog to cross your local loop (the two wires from your "telephone" to the > telephone exchange) and then it is converted to digital signals at the > local telephone exchange and delivered through the phone network to an ISDN > Primary Rate interface at the other end. Throughput from your computer is > at about 33.2Kbps. The data coming from the other end (which is a router or > access server connected to an ISDN network) does not need to be converted > from digital to analog because ISDN is digital. So data coming in from the > other end is sent at 56kbps. > > If you connect two 56K modems through the telephone system, they'll never > go faster than 33.2Kbps, as they are both having to do the digital/analog > conversions. Only when you connect to an ISDN device (e.g. at your ISP), > will the traffic to you be sent at 56K. Any kind of noise or attenuation of > signal will lower this of course. > > So "about half" is actually "about right"... > > Best wishes > > Chris Jaecker --------------------------------------------------------------------- To unsubscribe, mail [EMAIL PROTECTED] with the line: 'unsubscribe vnc-list' in the message BODY See also: http://www.uk.research.att.com/vnc/intouch.html ---------------------------------------------------------------------
