Ken said:
Having called VoIP a kind of landline, I was taken to task by a couple
of you here, Doing more research on the way the terms are used, it
appears that I was wrong and you were right. The name "VoIP" is
apparently not used the same way as the same as the term "landline."
See, for example,
http://science.opposingviews.com/difference-between-voip-landline-17888.html
But then I have question: what term can be used to describe all kinds
of plugged-in telephones (landline or VoIP) to distinguish them from
cellular phones?
The two _separate_ terms, exist for a reason.
If you say "VOIP" to me, it implies a transport of unknown origin,
with an IP layer carrying digital voice samples. VOIP can work
over broadband of some sort. It might even work over dialup,
assuming compression works well enough to do the job (otherwise,
a dialup connection wouldn't have sufficient bandwidth to do
the job). So if you say VOIP, I end up asking you for details
of the transport method.
A landline is baseband communications. The signal is analog,
and carried between 300Hz and 3.4KHz (passband). VOIP is not
the same thing. VOIP is not even a perfect "clear channel",
as attempting to FAX over VOIP, using a FAX modem, won't
work until you drop the FAX transmission rate below 14400.
The two terms cannot be mixed. Say "VOIP", if you mean
an unreliable digital means of emulating voice telephony
service. Say "landline", if you're referring to that
piece of copper running back to the Central Office, the
one that works between baseband 300Hz and 3.4KHz.
The landline, can have many signal types imposed on it.
1) 300 - 3400Hz analog conversation.
2) Low frequency ringer signal, high voltage (you'll get a shock!).
Never grab the wires on a phone line, when the telephone is about
to ring.
3) Minus 48 volts, to make traditional phones work.
4) ADSL signals, carried above 3400Hz, and separated
with things like the filters that come with your ADSL modem.
When a landline is used purely for ADSL, and no voice service
is wanted, that's called a "dry loop".
Paul