CUCM - Built-in-Bridge (system level)
Built-in-Bridge setting can be enabled on per-phone basis or on system level (default to all phones).
Access the System > Service Parameters menu option in Cisco Unified Communications Manager Administration, select your CUCM server from the Server list and Cisco CallManager from the Service list:
To enable Built-in-Bridge on system level, change the Clusterwide Parameters (Device - Phone) -> Builtin Bridge Enable optoin to On: