Central Office (CO)

Last Updated: June 29, 2012

Definition - What does Central Office (CO) mean?

A central office, in telecommunications, is a building to which subscriber home and business lines are connected on a local loop. This office has telephone switches to switch calls locally or to a long-distance carrier office.

This term is also known as end office or public exchange.

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Techopedia explains Central Office (CO)

Of major importance for equipment installed in a central office is uptime, network integrity, equipment compatibility and natural disaster survivability. Strict environmental and physical packaging requirements are defined by telephone service providers for telecom equipment manufacturers to ensure that switches and other central office equipment always continue to function.

The central office packaging testing requirements are defined by the Bellcore Network Equipment Building System in North America and the European Telecommunication Standard Institute in Europe. These are known as capability sets.

The central office code refers to the first three digits of local phone numbers.