Why are Comm. power systems positive ground?


Thread Starter

Jon Harms

Does anyone know the origin of the communications industry standard of tying the positive leg of their DC power systems to ground? Thanks for your answers.

Aaron Gelfand

According to one application note that I read on ECL/PECL circuits, tying the positive supply voltage on the chip to ground, and the
negative supply to -5 volts, results in much better noise rejection. I do not know for sure this is the answer for the communication
industry, but since it makes sense for the chip level, I could see it being adopted in this way.


Tomy Zacharia

Hi list,
One of the reasons to use a positive ground was to prevent corrosion on the long distance signal wires strung on telegraph poles. The tradition has been carried over to this day of optic fibre and satellite for long distance communications. The same principle that is used to cathodically protect metal structures, both overground and underground.
Tomy Zacharia
Telecom and Instrumentation Engineer