-48Vdc on telephones

[nolram]

hello everyone! I want to ask somebody out there to shed light on my questions: Why is it that landline telephone accepts -48Vdc? Why is it

 

[nitrojunx]

this is to avoid cathodic effect, that is -48volts with respect to ground...

 

[nolram]

thanks! I would be very appreciative of anybody who can give me links to tutorials explaining this... thanks again.

 

[walid1]

you can go to this link it is a rich text about telephones

http://www.epanorama.net/links/telephone.html

I hope this may help you

 

[nolram]

thanks walid!