| Network Topologies network topology is defined as: the schemes of joining a number of computers in the form of a network are called Network Topologies. Physical Transmission media In physical Transmission media, communication devices are directly linked with each other via cables or other physical materials for data communication. Twisted-Pair Cable It is one of the most commonly used communication media for network cabling. It consists of two separate copper wires that are covered by insulating material such as plastic and twisted together to form a cable. Coaxial Cable Coaxial Cable is also referred to as coax. It consists of a single copper wire surrounded by insulating materials. Usually, it is surrounded by three layers. -
Insulting material -
Solid metal shield -
External plastic cover
Fiber-Optic Cable In twisted-pair cable and coaxial cable, data is transmitted in the form of electric frequencies. So copper wire has to be protected from water and electromagnetic waves. In fiber optic cable, these types of problems are not occurred. The fiber-optic cable uses light to transmit data. A fiber-optic cable consists of hundreds of thin glass fibers or strands of glass. Each strand is referred to as optical cable. Wireless Networking In Wireless transmission media, communication devices communicate with each other and data is communicated through the air or space using broadcast radio signals, microware signals and infrared signals. This transmission medium is used when it is impossible to install the cables. The data can be transmitted all over the world through this medium. Broadcast Radio It is a wireless transmission medium that is used to communicate information through radio signals in air, over long distance such as between cities and countries. In this medium, a transmitter is required to send messages and receiver is required to receive them. To receive the broadcast radio signal, the receiver has an antenna that is located in the range of signal. Some networks use a special device called transceiver used to send and to receive messages in the form of radio signals. The data transmission speed of broadcast radio is up to 54 Mbps. Microwaves Microwaves are radio waves that provide a high speed transmission. In microwaves transmission, data is transmitted from one station to another. Microwaves station contains an antenna, transceiver and other equipments that are required for microwave communication. The data transmission speed of microwave transmission is up to 150 Mbps. Digital Modem The modem that is used to send and to receive data to and from a digital telephone line is called digital modem. ISDN modem and DSL modem are the best example of digital modem. These modem are used to send and receive the digital data to and from the digital line, So there is no need to convert to analog signals because digital lines already use the digital signals.
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