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Sử dụng điện thoại di động của bạn khi bạn đang đi từ khu vực dịch vụ di động của bạn, đi du lịch trong khác, được gọi là chuyển vùng. Hầu như tất cả các hãng di động đã thực hiện sắp xếp theo đó bạn có thể chỉ cần đến một khu vực dịch vụ khác hơn là của riêng của bạn và tự động bắt đầu sử dụng dịch vụ của nhà cung cấp. | The Cellular Connection A Guide to Cellular Telephones Fourth Edition. Robert A. Steuernagel Copyright 2000 John Wiley Sons Inc. ISBNs 0-471-31652-0 Paper 0-471-20340-8 Electronic 7 ROAMING Using your cellular phone when you re away from your home cellular service area traveling in another is called roaming. Virtually all cellular carriers have made arrangements under which you can simply arrive in a service area other than your own and automatically start to use that carrier s service. There is a certain mystery surrounding roaming and a lot of questions have arisen over what roaming is and how it works. This chapter is intended to answer those questions. HOW TO TELL WHEN YOU RE ROAMING The boundaries that mark the end of one cellular carrier s domain and the beginning of another s are invisible. Unless you ve traveled the route before you can t tell when you ve left your home area and entered another. But your phone can. One of the indicators on a cellular phone is labeled ROAM see Figure 6.1 . It serves several purposes. When you leave your home region and enter another the ROAM indicator will light and stay lit as long as you are within the range of a cell site. If you are between systems or out of range of the cell site of any system the ROAM indicator will go out and be replaced by the NO SERVICE iight as you pass through the area. 63 64 ROAMING The ROAM indicator serves another purpose. It will tell you when you are receiving signal from a carrier on a different frequency block from your home carrier. All cellphones are equipped to switch automatically between two services nonwireline and wireline or the A vs. B block carrier. The service you normally use is programmed in the phone s numeric assignment module NAM to give one priority over the other so that your own carrier will always be selected over the competitor in your area. On many phones you can program which carrier A or B is to have priority over the other yourself and even lock out the other .
