The US POTS is digitized at 8KHz sample rate, so Nyquist says the highest frequency you can accurately digitize is 4KHz. Allow some for a (fancy digital) filter and 3400Hz is about the best you can expect. As for T1, almost right. The 8K samples per second are u-law processed to 8 bits each for transmission down the line, at 1.544 Mb/s a T1 line handles 24 streams, plus 8K bits per second of supervisory data. Yes, a nice round 193 bits per frame.
Bob LaJeunesse >________________________________ > From: DaveH <i...@blackmountainforge.com> >To: 'Discussion of precise time and frequency measurement' ><time-nuts@febo.com> >Sent: Sunday, January 5, 2014 1:53 PM >Subject: Re: [time-nuts] WWV/WWVH audio simulator? > > >This is by design > >The POTS (Plain Old Telephone System) specifies a bandwidth of 300Hz to >3,400Hz. > >http://en.wikipedia.org/wiki/Plain_old_telephone_service > >They are trying to cram as many channels into as little bandwidth as >possible and the greater the frequency response they provide, the more >bandwidth it takkes and the fewer channels they can provide. > >T1 lines were originally developed to bring 16 voice channels into a >building that didn't have enough copper circuits. > >Dave > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
