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Digital technology in the telephone network is nothing new. Take all the relays in older exchanges as an example. Relays are either "off" or "on", and there is no state in between these. Suitable combinations of relays could build up and "remember" numbers - perhaps a far-fetched example, but in was digital, so it will serve! | HỌC VIỆN CÔNG NGHỆ BƯU CHÍNH VIỄN THÔNG BÀI TẬP TIẾNG ANH CHUYÊN NGÀNH ĐTVT (Dùng cho sinh viên hệ đào tạo đại học từ xa) Lưu hành nội bộ HÀ NỘI - 2006 HỌC VIỆN CÔNG NGHỆ BƯU CHÍNH VIỄN THÔNG BÀI TẬP TIẾNG ANH CHUYÊN NGÀNH ĐTVT Biên soạn : THS. NGUYỄN QUỲNH GIAO THS. NGUYỄN HỒNG NGA UNIT 1 Exercise 1. Read the following passage then answer the questions. ANALOGUE AND DIGITAL NETWORKS Digital technology in the telephone network is nothing new. Take all the relays in older exchanges as an example. Relays are either "off" or "on", and there is no state in between these. Suitable combinations of relays could build up and "remember" numbers - perhaps a far-fetched example, but in was digital, so it will serve! What is new is the transfer of speech digitally. In other words, the sound we make when we speak is converted to digits and sent out on to the network. In order for the person called to understand what we are saying, these numbers must be converted back to audible sound again. The audibility of speech transmitted in analogue form over long distances can be very bad. Due to, for instance, noise it may be difficult to understand or recognize what the other person is saying. But with a number, things are different. It would need very bad handwriting indeed to distort a "one" beyond recognition! So even if the one is distorted when it arrives, it can still be interpreted and recreated to give undistorted sound in the receiver. In analogue lines, the sound is amplified at regular intervals. The corresponding stage in digital lines is regeneration, i.e. the distorted number is interpreted and recreated. Herein lies an important difference between the characteristics of the two methods of transmission. In the analogue system the noise is also amplified. Every amplifying stage along the line leads to an accumulation of noise. In the digital system, the information is created anew at every regeneration stage, and can be sent on unaffected by the noise. A. Write True (T) or
