Calls made to or from a Business Group line are identified as internal (dialed from within the Business Group using an extension code) or external. Distinctive ring cadences, call waiting tones, and Caller ID can be used to distinguish between internal and external calls. Note that calls within the Business Group are treated as internal only if they are dialed using an extension code. If the caller dials the full directory number or a short code to call another line within the group, this is treated as an external call. Internal calls (extension to extension) will be a single ring. External calls will be a double ring.