Why does the telecommunications industry use -48 VDC with a positive ground?

The telecommunications industry employs -48 VDC with a positive ground primarily to mitigate electrolytic corrosion on the outside plant infrastructure. In environments where moisture and soil interact with electrical systems, the risk of corrosion can significantly impact the longevity and reliability of equipment.

By using a negative voltage with a positive ground, any electrochemical reaction that could lead to corrosion is minimized. This is particularly important for metallic components buried in the ground, such as copper or aluminum wiring and conduits, as these materials are susceptible to degrading over time when exposed to moisture and contaminants.

In contrast, using a different voltage configuration could create potential differences that may promote corrosion, particularly due to stray currents. Thus, this practice is not only a technical one but also a preventive measure to ensure that infrastructure investments in telecommunications remain viable over longer periods without requiring premature replacement or repair. Other reasons for employing this voltage standard largely revolve around safety and operational consistency, but corrosion mitigation stands out as a critical factor for maintaining the integrity of outdoor telecom systems.