A CDE Definition
The facilities within a telephone company's central office (CO). It includes the main distribution frames (MDFs), switches, digital cross-connects, add/drop multiplexers and other networking equipment. Contrast with outside plant. See central office.
A local telephone company switching center. There are two types of central offices (COs). The first is called an "end office" (EO) or "local exchange" (LE) and connects directly to the outside plant, which is the feeder and distribution system to homes and offices. The end office (often called a "Class 5 office") provides customer services such as call waiting and call forwarding.
The second type is the tandem office (also toll office or tandem/toll office), which is a central office that does not connect directly to the customer. Toll call record generation and accounting used to be handled in the tandem offices. Today, the billing is mostly done in the end offices. There are more than 25,000 central offices in the U.S. See LEC, IXC and LATA.
High-Tech Switching in the 19th Century
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