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Reply To: Why -48V is used as power for telecom?


HI every body,
I’m replying very late
Sammour has rightluy pointed about chemical effect.
Actually in olden days there was over head bare cables used for telephone systems & in order to reduce the chemical effect from halogens (which are the most one responsible for corrosion)which are -ve charged and are repelled by -ve voltage. Hence -V. The figure of 48 was taken becuse it was a compromise between safety (of electrocution) & power loss due to R of cables HENCE -48V