1. The IP PBXs in Beijing, Shanghai, and Guangzhou are connected to each other. Among the IP PBXs, Shanghai uses a SoftCo9500.
2. Beijing, Shanghai, and Guangzhou have their own four-digit extension number. Extension numbers may overlap.
3. Prefixes 422, 406, and 405 are added before the Beijing, Shanghai, and Guangzhou outgoing numbers, respectively.
When a user places a call from Shanghai to Guangzhou, the calling number prefix can only be configuredto 405.