[time-nuts] WWV/WWVH audio simulator?

Robert LaJeunesse rlajeunesse at sbcglobal.net
Sun Jan 5 14:33:02 EST 2014


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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