# Extensions

Extensions are a 3 digit identifier from the range 500 -- 599.

End users on your Business Phone System are assigned a unique Extension to manage their inbound and outbound call routing.

An internal end user on your Business Phone System can contact another internal end user by simply dialing their Extension.

Extensions can be configured within the Call Flow Features: Call Queues, Ring Groups, Auto Attendants and Redirection Triggers.

If you require additional Extensions, you will need to contact your service provider and request additional Extensions be added to your Business Phone System.

Refer to How to Configure Extensions.