On Wed, Jun 30, 2010 at 3:06 AM, ALAN GAULD <alan.ga...@btinternet.com> wrote: > > >> > If its a typical ADSL line it will be conneced to a DSLAM at >> > the centeral office(by the telco) and that will be shareed. >> >> > ADSL also loses bandwidth the further you are from the office > >> process has to be diversified for each customer, because it >> all travels at the speed of light. > > It is diversified on the individual line leading to your house > but it is shared from wherever it gets converted to a digital > multiplex. That could be at the roadside cabinet or at the > central office. At that point the data is mixed together > using a round-robin type algorithm. The more active signals > that are present the lower the proportion of the total bandwidth > available to each. > > The speed of transmission is not really relevant (it only affects > transit time not bandwidth) although it is as you say the > speed of light (but not the speed of light in a vacuum, much > lower than that) within the bearer. However within the electronics > the signal travels more slowly - around the speed of sound - but > fortunately for very small distances. > >> sometimes had a weak signal depending on the distance >> from the consumer. This signal could be modified from the cable >> company, so the box amplified the 'weak', but not further away, >> signal. > > Its not a matter of signal strength but of signal smearing as it > travels along the line. The digital data is sent as pulses (a great > simplification!) but those pulses lose their shape as they travel > along the line until eventually the electronics cannot distinguish > one from another. The only way to improve is to send the > pulses more widely spaced, which reduces the bandwidth, > or to have repeater boxes which regenerate the pulses at > regular intervals. On long distance routes, between cities, the > telco will install repeaters but for domestic use they progressively > reduce the bandwidth. > >> So this would also be a matter of what was being sent/received >> being modified, depending on the priority (given by the ISP provider) >> of the current DSL (or whatever connection) consumer? > > No, it doesn't matter what priority the comnsumer has it is down > to the physical characteristics of the line. Telcos typically use > copper or aluminium conductors in the local lines with paper > or PTFE insulation and either crimped, twisted or soldered joints. > All of these affect the transmission characteristics but the biggest > factor is the length of the line. Its not economical to install > repeaters in every consumer line so the bandwidth must be > adjusted to match what the line is capable of. (This is done > dynamically so you may even find your bandwidth varies slightly > depending on the weather!) In practice it should be fairly stable > and the biggest variations will be due to contention at the > DSLAM. > > HTH, > > Alan G. > (Who works for a telco! :-) > >
Thanks for taking the time to answer, and sorry for somewhat hijacking the op's thread. _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor