JJ wrote:
On Sat, 26 Aug 2017 01:39:06 -0400, wrote:
I have a dual core XP machine and my dial up connection stopped
working. I have tried 3 different Win Modems. The modems install OK
and the diagnostics say it is connecting OK but when I try dialing
out, I get the message that there is no dial tone. That phone wire
works in a phone (same wire that plugs into the modem) I can also plug
a phone into the other port on the modem and dial out through it. I
tried swapping ports to be sure it wasn't just labeled wrong.
There is no activity on the line when I listen from another phone.
Any ideas?
If I'm not mistaken, land line telephone system has more than one standard.
Similar like TV signal standards e.g. NTSC-only or PAL-only on old TVs,
except that most TV nowadays support both standards. Or 110V vs 220V power
source standard in countries. Phones/faxes/modems only support one standard,
AFAIK. If this is the case, perhaps your modems aren't built for the phone
system used in your country.
It's true that standards differ *between countries*,
but a consistent standard is used within a single country.
Battery in North America is nominal -48V.
Battery in Brazil is -80V.
The thresholds for off-hook will differ too, from
country to country.
There were two standards for digital data samples.
ulaw and Alaw. One used in North America, one used
in Europe. This is a scheme for dynamic range
compression, using a limited number of bits in
a voice sample, to give what is effectively more
bits of resolution to handle the dynamic range of
a call.
But within a single country, all the equipment works
to the same standard.
When they make the chip for the Line Cards (for POTS),
the chip is fully programmable at the register level.
It handles on the order of 20 different configurations
that cover the entire world. They don't have to
change cards because they're in Brazil, and one
design handles everything. You just have to program
it correctly before turning it on.
You can program it for Brazil, or you can program
it for North America. This makes the equipment using the
card, "universal".
If a business has a PABX (private automatic branch exchange),
the interface on that can be custom. A different connector
might be used in the cubicle. Normally there will be
warnings about plugging consumer gear into it.
So not every telephony problem has a simple solution.
But at least for consumers, normally you're dealing
with telco interfaces, and they're all using
the same standard.
A technician can wring out a telco line remotely, to get
some idea if the line is wet or whatever. And then
file a trouble ticket if line maintenance is required.
At the consumer end, you can do your part by re-wiring
the telephone. For example, my in-home wiring had
a corrosion problem with the receptacles near the
carpeting. I went downstairs, and disconnected
that network at the demarc. I got some four-wire
cable at my (only) electronics store (not a Radio Shack),
bored a hole in the floor in a closet, and ran a wire
up to the computer room from the demarc. Then, I had
flawless telephony and my problem was solved, and
all without a $99 truck roll with Bell. Many of the
problems with POTS, are in your house, and not actually
a problem on the pole.
My network here, used to consist of buried cable from the
CO to the corner of my street. And elevated phone wires
on poles, from the corner to each house, following
the right-of-way provided for utilities on the
back property line.
Since the advent of fiber optic transmission (replacing
the fat copper wire bundle, with a slim fiber to the
same Central Office), the failure rate is a lot lower.
The fat bundle of wires, needed to be "dried" at regular
intervals. A phone truck would show up with cylinders of
dry nitrogen gas, to flush the underground line.
Once fiber equipment replaced the punchdown blocks
and pedestals at the end of the street, reliability
went up. And the five hundred foot run of elevated
wire, seems to be quite good.
Paul