In telecommunication, a common battery is a single electrical power source used to energize more than one circuit, electronic component, equipment, or system.
A common battery is usually an electrolytic device and is usually centrally located to the equipment that it serves. In many telecommunications applications, the common battery is at a nominal -48 VDC. A central office common battery in the battery room supplies power to operate all directly connected instruments. Common battery may include one or more power conversion devices to transform commercial power to direct current, with an electrolytic battery floating across the output.
This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C" (in support of MIL-STD-188).