An administrator is tasked with deploying a server in a telephone switching station. Which of the following voltages will MOST likely be available at the facility?

-48VDC is the universally recognized standard distribution voltage in telephone switching stations and central offices. The negative polarity was historically chosen to reduce electrolytic corrosion on copper conductors, and the 48V level offers a safe, efficient supply voltage for telecom gear over long internal cable runs. Any server deployed in such a facility must be compatible with, or powered via conversion from, this -48VDC plant.

120VDC is not a recognized telco facility distribution voltage; telecommunications DC plants operate at -48V, not 120V.

220VAC is a standard commercial AC voltage used in many countries for general building power but is not the characteristic supply of telephone switching stations.

440VAC is a high-voltage 3-phase AC supply used for heavy industrial motors and large HVAC equipment, not telecommunications infrastructure.