Telco Central Office, where telecommunications equipment is located.

Central Office. The central office of the public switched telephone network that handles the routing of calls in a specified area.

Central Office.  A building in which telephone companies and similar operations locate their switching equipment and terminate their circuits to interconnect with each other, with end users, and with trunk lines.  Sometimes the central office will also be referred to as the exchange.

A CO (center outlet) lavatory waste fitting for a sink with no overflow channel.

Official title of the captain of a Navy ship.