[time-nuts] WWV/WWVH audio simulator?
DaveH
info at blackmountainforge.com
Sun Jan 5 19:57:55 UTC 2014
DERP -- you are right. T1 does 24 voice channels, not 16.
Thanks for the heads up!
Dave
> -----Original Message-----
> From: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Robert LaJeunesse
> Sent: Sunday, January 05, 2014 11:33
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] WWV/WWVH audio simulator?
>
> 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 <info at blackmountainforge.com>
> >To: 'Discussion of precise time and frequency measurement'
> <time-nuts at 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
> >
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