On Thu, 10 Jul 2003, Nick Rout wrote: > On Thu, 10 Jul 2003 07:50:47 +1200 (NZST) > Mahesh De Silva <[EMAIL PROTECTED]> wrote: > [...] > > On our current ADSL we max out around 400k down. > > > > I think the speed issues is due to the distance from > > the exchnage. I didn't think ADSL suffered the same > > problems as cable where it shares the pipe. > > same here i thought, as each user has their own piece of copper going > all the way to the exchange.
Thanks for the info, Mahesh and Nick. 400 k sounds much more like real life for residential ADSL to me. Yes, cable length is one of the major limiting factors. As for "your own copper", the matter is a bit more complicated. While it is correct that each subscriber is connected to the local exchange via an individual twisted pair of copper wires (unless there is a kerb-side multiplexer), there is still an issue with the "neighbours". Telephone cables are normally buried along the road, and these cables are bundle cables which contain a large number of individual twisted pairs. The smaller cables have 50 twisted pairs, the fat ones much more. Since the twisted pairs inside the cable are not shielded (the twist works as shielding for really low frequencies), there is significant crosstalk between neighbouring pairs inside these cables. The higher the frequency, the more crosstalk you get. These cables are not designed to be used at ADSL bandwidth on all pairs. Originally they were meant to be used for the voice spectrum up to 3.4 kHz. That is the background of my initial question whether anyone knew how Telecom guarantee 2 Mbps, and whether they really keep the promise... And cable TV networks and Internet access, yes, another story where much more trouble is buried than any network operator would openly admit. And power line communications, grmbbblll, grmbbll,... Kind regards, Helmut Walle. +----------------+ | Helmut Walle | | [EMAIL PROTECTED] | | 03 - 388 39 54 | +----------------+
