A smaller, localized switching module that operates under the control of a larger, central exchange or core router. It aggregates traffic from endpoints, handles internal routing for local calls or packets, and forwards long-distance or external traffic up the hierarchy to the main switch. This architecture reduces the required trunk capacity between remote facilities and the central office.
Heard on the job
All the extensions in the annex are wired to a subswitch, which connects back to the main PBX over a single fiber trunk.