Telecommunications_and_Networks

Telecommunications_and_Networks - AB113 Information...

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AB113 Information Technology Telecommunications and Networks 1. Fundamentals of telecommunications Communications may be defined as the transmission of a signal (containing a message comprised of data and information) by way of a medium, from a sender to a receiver. Both sender and receiver must understand the signals and agree upon the way the signals are to be interpreted. Telecommunications refers to the electronic transmission of signals or communications. Data communications is a specialized subset of telecommunications referring to the electronic collection, processing, and distribution of data, typically between computer system hardware devices. A telecommunications network connects communications and computing networks. A computer network is a specific type of telecommunications network that connects computers and computer systems for data communications. 2. Data Transmission 2.1 Signal Types The faster the signal frequency (measured in Hertz), the faster the data transmission (bits per second). Analog Signals - Continuous fluctuation over time between high and low voltage - Transmitted as sound waves along a channel such as copper telephone wire. Digital Signals - Discrete voltage states transmitted as a series of bits or on/off signals. (high for 1 and low for 0) Modulation - Conversion of digital signal to analog signal - Frequency and amplitude modulation - Modems modulate and demodulate signals Computer 1 Computer 2 Modem Modem Digital Signals Digital Signals Analog Signals Modulation Demodulation
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2.2 Bandwidth The range of signal frequencies that can be sent over a given medium at the same time is known as the bandwidth. Width or capacity of the communication channel. Measure of transmission capacity (bps, kHz and MHz) Data channels - Narrowband (< 64kbps) (Dial-Up Modem) - Wideband (64kbps - 1.544Mbps) (Special Leased lines connect minicomputer/mainframe) - Broadband ( >1.544Mbps) (DSL/Cable/Satellite Connection) 2.3 Protocol A communication protocol is essentially a set of codes or conventions used for facilitating communications between hardware and software. 3. Media Type 3.1 Physical Cables Twisted-pair cable - Consist of two or more pairs of twisted copper wires. - Twist helps keep signals from “bleeding” into the next pair. - Twisted-pair wires are insulated, hence, can be place close together and packaged in one group. -
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Telecommunications_and_Networks - AB113 Information...

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