Answer / r. d.

- 48 VDC is used in telecom to prevent corrosion or
electrolysis. If you use +48VDC there are free electrons
raging to go somewhere, as each electron is lost, you lose
what is part of a molecule of copper, thus the copper
corrodes away, lines corrode away until they break! -48VDC
wants electrons so it attracts molecule = no loss of copper
or corrosion/electrolysis.

Answer / k.prakashchandra

positive is earthed ?

Answer / cnu

Basically for any electronic device it needs a DC supply as
a source power the different components inside it.
everybody knew that the telephone in our houe will not
contain any supply line (speaking about basic model) other
than the one that comes from the exchange. but how is the
Electronic board inside the telephone is working?

this line carries a DC voltage of 48V (42V to $8V approx).
this voltage supplies power to the components inside the
telephone as well as carries the voice signals from
exchange to our phone and vice versa.

Answer / shivareddy

Equipments which is used in telecom field Designed
for -48volts

Answer / vinayak.kadam

no idea???

Answer / ratikanta mekap

because all of the electronics equipments used in telecom
field(bts,tx-rx rack,mux etc)are working in dc supply,so
that this is happen.

Answer / u.chandarasekar

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