A central office is a telecommunications facility into which all local residential and business phone lines converge and are connected to switches that enable phone service. They are also called telephone exchanges and switching centers and are telecom's version of an electrical substation.
"Office" is a bit of a misnomer and a throwback to when central offices were populated with dozens of switchboard operators who would connect callers to their destination numbers. Now, with automatic call connections, central offices are filled with racks of hardware and tens of thousands of cables. Employees are mostly engineers.
Central offices are designed for maximum uptime, which means they're disaster resistant. The phone lines that go into central offices have been buried underground for decades to mitigate the negative effects of snow, ice and wind. Now, many central offices are also being built underground not only to protect them from disasters, but also to protect the surrounding area from the electromagnetic radiation they emit.
Due to the importance of quality voice services, central offices are an important component of the contact center ecosystem.
