Có 15+ tài liệu thuộc chủ đề "bài giảng viễn thông"
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For the computer and the modem interfacing the standard is the RS-232.. Procedural - sequence of events for transmitting data EIA RS-232 Interface Standard:. EIA232 was first started in 1962 as RS-232 by the Electronics Industries Association (EIA) published in 1969.. RS-232 defines the electrical, mechanical, functional, and procedural interface between DTE and DCE.. The RS-232 mechanical specification states that...
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A digital signal is comprised of a number of signals. The third harmonic is one third of the amplitude of the base frequency (also called the fundamental frequency), the fifth harmonic is one fifth the amplitude of the fundamental and so on.. In order to send a digital signal across a voice channel, the bandwidth of the channel must allow...
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The process of converting analog signal to digital is also known as A_to_D conversion or A/D conversion. Pulse modulation:. Pulse modulation can be subdivided into two groups:. Analog pulse modulation. A periodic pulse train is used as the carrier wave, and some parameter (amplitude, duration, or position) of each pulse is varied in a continuous manner in accordance with the...
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The Telephone System: (Ref: Ch-4, Page-113 of your Text book). The telephone system remains as the backbone of low-cost telecommunications services in North America. An understanding of the telephone system is necessary when considering its use for data communications.. Single wire: In the beginning, the market was for telephones only. Copper: At one time, 80% 0f AT&T's capital was the...
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Circuit switching. Message switching (using store-and-forward network).. Packet switching. The actual service offered is connection oriented, but it is implemented internally with packet switching.. Circuit switching:. Message switching:. Instead, it is sent and stored in the first switching office (i.e., router) and then forwarded later, one hop at a time. Packet switching gets round this problem.. Packet switching:. In Packet...
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This time-sharing is known as Time division Multiplexing (TDM).. Second, the bandwidth of the microwave link can be divided among logical channels, with each user having exclusive possession of some frequency band. This sharing by frequency band is known as Frequency division Multiplexing (FDM).. Multiplexed circuits generally have to have the same capacity (bandwidth) as the sum of the circuits...
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Data Communications:. Dictionary Meaning of the Word Telecommunication:. The information that is transmitted can be in the form of voice, symbols, pictures, or data, or a combination of these. To fulfill the occupational need of the society:. One of the most famous events of "telecommunications". In September 490 BC a terrible battle was going on at the coast of the...
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Error Sources, Detection and Correction The Data Link Layer. Echo suppressers are used in the telephone system on long distance calls. Echoes are caused by impedance mismatches in the telephone equipment. Error Detection:. Error detection involves sending extra information with a message (frame, packet, block, etc.) which is used by the receiver to determine whether the data has been received...
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Communication happens in the form of signals.. The more changes in the signal, the more information that the signal can convey.. An electromagnetic signal is a function of time, but it can also be expressed as a function of frequency.. The frequency-domain view of a signal is far more important to an understanding of data transmission than a time-domain view.....
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Any periodic waveform can be expressed as the sum of sine waves with frequencies at integer or harmonic multiples of the fundamental frequency of the waveform and with appropriate maximum amplitudes and phases.. Reed organ is also called Harmonica, as the reeds are tuned to vibrate at harmonics of the fundamental signal.. Spectrum, of a signal is the range of...
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Các dịch vụ vận chuyển hàng không. Dịch vụ mạng phi liên kết băng rộng (trong ATM) BCOB Broadband Connection-Oriented Bearer Service (ATM). Dịch vụ mạng băng rộng. Dịch vụ mang. Hệ thống trạm gốc. Dịch vụ vệ tinh quảng bá. Dịch vụ truy nhập không dây. Dịch vụ mô phỏng mạch. CL Connectionless Service (ATM) Dịch vụ không kết...
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ố ặ ộ ọ 3.6.1.3 C u trúc ch c năng c a ATM ấ ứ ủ. B ng 3.4 trình bày các ch c năng đó. B ng 3.4: ả Ch c năng các l p c a B-ISDN ứ ớ ủ. 3.6.2.2 Ch c năng c a l p ATM ứ ủ ớ. T o và tách tr...
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Hệ thống ghép kênh sơ cấp có hai phân cấp. .1 Hệ thống PCM 24 (USA &. Hệ thống ghép kênh PCM Bắc mỹ và Nhật sử dụng các từ mã 8 bit và lượng tử theo quy luật =225, tốc độ truyền dẫn của hệ thống là 1544Kb/s và có thể được sử dụng như luồng bit đầu...
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Tìm hi u v c ng LPT- ể ề ổ Line Printer Terminal. Nguy n Th H ễ ị ườ ng ĐTVT-K8A 5. Máy tính có ng d ng nhi u nh ề ự ế ạ ề ể ế ị ứ ụ ề ư v y do nó có th ghép n i v i các thi t b ngo...
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Cũng chính nguyên t c đó cùng v i nguyên t c t đ nh đo t c a ồ ắ ớ ắ ự ị ạ ủ vi c gi i quy t tranh ch p đã chi ph i toàn b quan h trao đ i c a ệ ả ế ấ ố ộ ệ ổ ủ n n...