SNET's coax sub-nets require between 500 watts and three kilowatts of continuous power. This means that a typical central office that supports 30,000 lines is faced with supplying an additional 300 kilowatts of power at the node. Losses in the UPS systems-typically resulting in 90 percent UPS efficiencies. Power factor losses in the distribution system-currently not measurable, but anticipated to be no more than a few percent. Losses in the power node-limited to about 6 percent through the use of a reliable and efficient controlled ferroresonant transformer system.
Total efficiency is the product of all the contributing efficiencies.
Multiplying the above efficiencies together results in an overall efficiency of about 65 percent, which means that the central office is required to provide the capacity of roughly 450 kilowatts. A reliable centralized powering system requires a highly reliable central power supply. Fortunately, within telephone companies, reliable central office powering is a well developed technology. Extending or replicating existing central office systems with redundant parallel UPS systems backed up by batteries and redundant motor generator sets can provide such reliable systems. Many of the components required in these new central office systems are catalog items.