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-48 V DC in Telecom Equipment

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Vasuki soni - 18th October 2014  (07:22 GMT)

Can negative voltages be used in other domains like power systems preferably to protect equipments from lightning and noise as has been identified in above comments..

gyan - 5th August 2014  (16:02 GMT)

It is -48 V D.C cause of the commercial battery stack available. Commercial battery stack is available in -12 V, -24 V or - 48 V. For info, actually any telecom equipment or for that matter any sophosticated equipment runs on a range of supply voltages by using their own inbuilt SMPS and it is very difficult to maintain a constant voltage by the power source.

BIBHUTI BEHERA - 3rd August 2014  (15:22 GMT)

1* In negative voltage due direct current less noise occurs... As a result telecom equipment gives high output..
2* corrosion less on eqiupment

3* It protect the equipmet fom lightning.

Abid Hussain Khan - 1st February 2012  (05:40 GMT)

Hi everybody,

Thanks to all for clear my confusion about why telecom equipment use -ev voltage but my question is why it is 48vDC (2*24), why not 50vDC (2*25)??

is there any restriction for DC voltage supply?

MRG - 8th February 2011  (11:16 GMT)

(i) Positive voltages cause comparatively more corrosion in metal than negative voltages.
(ii) Negative voltages are safer for human body while doing Telecom activities.
(iii) Lightning may cause positive voltages in the equipment circuitry. In that case, negative voltages (lack of electrons) neutralize positive charges and prevent excessive heat.
(iv) Negative voltage is safer for long telephone line for transmitting power trough it.

Lalit - 19th January 2011  (10:35 GMT)

Basically many reasons bt first is that noise and intrefrence is min at -ve supply voltage and second is that to protect from lightning

vasanth - 2nd January 2011  (07:49 GMT)

why we are using -48v...
1.pulse
2.moisture
3.earthing(lightening effects)

dextur - 21st November 2005  (00:19 GMT)

hello ranjeet,

i believe it is -48 to avoid cathodic reaction. You can read on this in the book Telephony by HARB.

Shaleen Srivastava - 14th October 2005  (08:30 GMT)

hi suku
actually this reason which i had told about the +ve supply ,told by one guy from philipines he is expert in telecom
i'll try to find ur answer and get back to u soon
can u please give me ur email id
mine is
srivastava.shaleen@gmail.com

suku - 13th October 2005  (17:09 GMT)

Hi Shaleen,

I have seen Motorola BTS , BSC , XCDRs have a positive +48V design also .

in this what will happen .

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