Why Telcom Equipments are fed with -48V

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SUMMARY

Telecom equipment predominantly operates on -48V instead of +48V due to anti-corrosion properties. A positive voltage on metal wires promotes corrosion, while a negative voltage relative to earth mitigates it. This design choice ensures uniformity across equipment, eliminating the need for separate local and remote versions. Even rack-mounted telecom equipment adheres to this standard to maintain compatibility and reliability in various environments.

PREREQUISITES
  • Understanding of DC voltage principles
  • Knowledge of corrosion effects on metal wiring
  • Familiarity with telecom equipment standards
  • Basic concepts of electrical engineering
NEXT STEPS
  • Research the impact of voltage polarity on corrosion in electrical systems
  • Explore telecom equipment design standards and specifications
  • Learn about power distribution methods in remote telecom installations
  • Investigate the role of -48V in enhancing equipment longevity and reliability
USEFUL FOR

Telecom engineers, electrical engineers, and professionals involved in the design and maintenance of telecom infrastructure will benefit from this discussion.

Telco
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Almost all Telecom Equipments are fed with -48V why not +48V?
 
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Anti-corrosion. Originally the DC power was fed down the telephone wires to power remote equipement a +ve voltage on a metal wire encourages corrosion a negative voltage (relative to earth) reduces it.
For equipment inside the electronics rack it doesn;t really matter.
 
Hi
But even Telecom equipments (Rack type) are working with -48V..
Is it the same reason or any other specific reason for that??
 
Telco said:
But even Telecom equipments (Rack type) are working with -48V.. Is it the same reason
Yes, you don't want to have to build a local and remote version of the same kit.
And even kit in a rack might be put out in a street corner box and fed from a central exchange.
 

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