In article <[EMAIL PROTECTED]>, [EMAIL PROTECTED] (Hal Murray) wrote:
> >> The telephone companies tend to be very aware of time and timing. The > >> time division multiplexing of T1 and T3 lines requires splitting the > >> second very precisely. Cellular phones also require very precise > > > >That can be true of the public network, although even then it may > >be more so for the more engineering oriented layers, like bearer > >synchronisation, than the more commercial oriented layers, like > >call detail recording. > > > >However, it is very definitely not true of most PABX systems, which > >typically have wristwatch and eyeball set times and run in local > >time, with no automatic daylight saving switch, and have no high quality > >frequency standard. > > There are two separate issues: time and frequency. > > Anybody know if I can get a good frequency off a DSL line? > Assume I'm willing to hack a wire into my modem/router. > > If so, it might be a nice/cheap way to get a stable clock > to use with a NTP box. (Handwave, PLLs and such. Not a hard > problem.) I assume that DSL follows a public standard, and that this standard will specify how good the clocks must be. For comparison, broadband cable modems follow DOCSIS 2.0, available from <http://www.cablemodem.com/specifications/specifications20.html>. My understanding is that both are timed protocols of some kind, but I don't know the details. Joe Gwinn _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
