Computers in the central office-a primer on powering equipment from -48 V

The convergence of computing and telephony is blurring the distinction between the two worlds. It is not unusual to have computing and data networking equipment installed in telephone central offices. This means that computing equipment is being adapted to operate from the -48 VDC central office (CO) power rather than the AC mains. This paper is a primer that provides an overview of what is required to power equipment from central office power. It reviews the fundamentals of central office power and distribution, the requirements of the two major standards agencies, Bellcore and the European Telecommunications Standards Institute (ETSI), and some implementation issues when equipment must designed to operate from either central office or mains power.