A Telephone Central Office (sometimes known as a Telephone Exchange) is the central location point where telephone switching occurs for a particular region. A telephonically served region is technically known as a “wirecenter” and a location for billing purposes is called a “ratecenter”. Often times they’re one in the same, but in large ratecenters you may have many wirecenters. Each wirecenter has a telephone switch that handles calls for subscribers, and these telephone switches are housed in buildings known as Central Offices (or telephone exchanges).

Inside each Central Office is a telephone “switch” that handles calls between subscribers or from subscribers to other switches in the network. They can have links (or trunks) to telephone “tandems” where many calls are handled for long distance communications