tailieunhanh - The Cellular Connection 2 phần 3

AN TOÀN Bất cứ điều gì đó khiến bạn lái xe có thể là một mối nguy hiểm. Một điện thoại di động, trừ khi nó được sử dụng với việc chăm sóc, có thể được như một phân tâm. Sử dụng một chiếc điện thoại cùng một lúc bạn đang cố gắng tập trung vào con đường và điều kiện giao thông có thể gây nguy hiểm cho cả bạn và các trình điều khiển khác. | 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 12 INTO THE FUTURE The technology that permits us to put telephones in our cars and in our pockets continues to evolve and provide us with new and improved services. Because there is no need for utility poles conduit or miles of expensive cable cellular telephones can be located either permanently or temporarily wherever they are needed. This versatility gives cellular the crucial economic edge that ensures the rapid growth of this new industry. In this chapter we will look into the future of wireless telecommunications and its applications. DIGITAL CELLULAR New technology permits the radio portion of cellular to become digital. From the carrier s perspective digital technology allows more channels than analog and thus greater capacity in the cellular system. From the user s perspective digital transmission will provide several advantages. First digital encrypts the conversation automatically providing even greater privacy of communication. But more importantly digital provides clearer audio and more consistent radio communication. Besides improving the audio fidelity of communication the background noise level will be reduced and static interference and other competing noises that occasionally occur in the transmission are virtually eliminated making the connection much 113 114 INTO THE FUTURE clearer. Finally and perhaps most importantly batteries last much longer on a charge using digital cellular. This is a very important advantage to people who use their cellular phone frequently. Digital cellular is probably available in your area. In order to make the transition cellular phones that are capable of both standard analog as well as the new digital transmission are usually used. These are commonly called dual-mode cellular phones and are available in all types portable transportable .