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Why -48 volts are used in Telecom?

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Question added by Adeel Mohi Ud Din , Team Lead Field Maintenance Access Network GSM & 4G-LTE , Ericsson Pakistan (Pvt.) Limited
Date Posted: 2017/09/27
Adeel Mohi Ud Din
by Adeel Mohi Ud Din , Team Lead Field Maintenance Access Network GSM & 4G-LTE , Ericsson Pakistan (Pvt.) Limited

Reason 1:

When interference is occur in voltages it affect only positive pulse not in negative terminal so if we make positive common then no interference occur And we get pure -48 volts without any interference.

 

Reason 2:

 

Because 2 terminal comes out from the battery and through red wire we ground the +ive terminal so that possibility of noise interference will get zero....noise occur only in the +ive terminal.....that’s why we use -ive voltage.

 

Reason 3:

All the electrical surges and noises are +ve in nature, when we give -ve polarity then negative supply neutralizes these noises & surges thus reducing false triggering effect.  

Reason 4:

By using negative polarity the cable doesn’t rusted or oxidized thus remains for longer life, but cable diameter get reduced in 15 to 18 month, so cable will be change.

 

Reason 4:

To prevent the equipment from lightning strokes because the cloud is negatively charged at bottom it requires a zero or a positive potential to discharge, and it selects the ground (Zero potential) to discharge. If the Telecom Equipments are fed with positive the cloud will choose the low resistance tallest positively charged Antenna's to discharge, this could damage the entire setup of Telecom equipments. So the Telecom equipments are fed with Negative supply Voltage

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