[time-nuts] WWV/WWVH audio simulator?

Jim Lux jimlux at earthlink.net
Mon Jan 6 23:43:05 EST 2014


On 1/6/14 8:36 PM, Magnus Danielson wrote:
> Bob,
>
> It works the other way around. The standard Bell handset (103A I believe
> the designation was) has the 300-3400 Hz response, and with not so fancy
> analogue filtering, you can handle 4 kHz and thus 8 kHz sampling rate.
> The ITU-T G.711 A-law (where naturally the americans wanted their own,
> so u-law appeared) does non-linear pseudo-dynamic compression into 8
> bits. T1s cram 24 channels into one frame, and adding 1 bit for framing,
> giving 24*8+1=193 bits per frame, giving the 1544 kb/s rate. 193 being a
> prime have caused a bit of headache over the years. In Europe, cramming
> 30 channels into a bundle was preferred, and allowing 2 bytes for
> framing and signalling. In T1, you do signalling by bit-stealing every
> 6th LSB on a channel. Caused some grey hairs for modem designers back in
> the day, and followed along over into the ISDN, as the primary rates was
> over E1 and T1. T1 also had three different line-encodings, of which
> only one was really transparent to all binary combinations.
>
> Oh the joy of early digital telephony. Many lessons where hard to learn.
> Synchronization was only one of them.

Don't forget the length of ATM cells.. 53 bytes.. because of how big 
France is.




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