The market is more about the metropolitan size (and by extension the number of TV's). (sbnation.com)
The principal came in for a visit and noted that the class was showing good behavior and told me what extension number to call should any problems arise. (educationworld.com)
With VoIP, each teacher can be provided with an extension number usable from all connected devices (including wireless), meaning they are always reachable wherever they are. (qaeducation.co.uk)