Why -48V?

[haylin1217]

None English deleted.

Moderator.

 

[bigkim100]

You really should not attempt to type when you are having a seizure...nobody can understand you.

 

[schmitt trigger]

?
How do you expect to receive an answer form a question that cannot be understood?

 

[SPDCHK]

None English deleted.

Moderator...

Speaka da English?

 

[smanches]

Interfacing Audio and POTS

Look at Note #4 at the bottom of the page.

BTW, I think he's speaking Tagalog (Philipino)

 

[Externet]

If I get what you are asking, telephone lines use 48 V because is in the limit considered safe for handling (low voltage) and negative because that way reduces electrolytic erosion of copper wires often wet when underground or rains.