RadioBanter - View Single Post - A more rational approach -- how I would like to change the cell phone industry.

D Peter Maus

Don Bowey wrote:
On 8/26/07 9:21 PM, in article
, "D Peter Maus"
wrote:

Brenda Ann wrote:
"John Navas" wrote in message
...
POTS phone lines are very limited. IIRC from my work with those systems,
about 300-3600 Hz. Strictly human voice range, not meant for hi-fi.
Special
lines are still available for hi-fi use as audio STL's.
POTS lines are encoded at 64 Kbps, which is why V.90 modems work, and
which is sufficient for decent audio, albeit not "hi-fi".

POTS lines are not encoded at all. Hence "Plain Old Telephone Service" which
can be used with any telephone (ain't no decoders in a WE 500 deskset) that
uses a DC line.

In the US, the telephone network has been digital since 1962. At the
time of the conversion, there was a decision made to keep the instrument
and the interface familiar to the user, so there is no conversion in the
deskset, and the 'last mile' from the CO is still analogue with battery
voltage as it always has been. But behind that interface, the network is
digital.

Now, that 'last mile' analogue circuit can be VERY poor. In my area,
a v.92 modem will only pass 14.4. While only a mile up the road, I was
getting 53k+ on the same v.92 modem.

When the network was converted from analogue to digital, there were
complaints that voices no longer sounded right and that some people
didn't sound like themselves. The complaints reached suce a pitch that
AT&T launched a PR campaign in which TV spots attempted to explain the
change in the audio at the instrument. As was the style of the times,
they didn't really explain anything, certainly nothing as technical as
digital audio, but instead, they described, through narrative and
animation, how a person speaking into a telephone would connect to the
central hub, where a voice that was similar to the speaker's voice was
selected, and sent on to the far end. That's why someone didn't sound
like themeselves.

No one bought it, of course, what with AT&T's reputation, by that
point...but it was a hilarious exercise in TelCo spin.

And paved the way for the explanation of 'Tru-Voice' 30 years later.

Yes, POTS lines are encoded. At the CO. The only thing POTS about a
POTS line is what sits on your desk, and a length of copper to the network.

You ignored pair-gain multiplexing in the Exchange Plant, which uses the
same codecs as are used in the message network.

Um.....no, actually, I didn't.