Los medios de transmisión son las vías por las cuales se comunican los datos. Dependiendo de la forma de conducir la señal a través del medio o soporte físico, se pueden clasificar en dos grandes grupos: \n* medios de transmisión guiados o alámbricos. \n* medios de transmisión no guiados o inalámbricos. En ambos casos las tecnologías actuales de transmisión usan ondas electromagnéticas. En el caso de los medios guiados estas ondas se conducen a través de cables o “alambres”. En los medios inalámbricos, se utiliza el aire como medio de transmisión, a través de radiofrecuencias, microondas y luz (infrarrojos, láser); por ejemplo: puerto IrDA (Infrared Data Association), Bluetooth o Wi-Fi. Según el sentido de la transmisión, existen tres tipos diferentes de medios de transmisión: \n* símplex. \n* semi-dúplex (half-duplex). \n* dúplex o dúplex completo (full-duplex). También los medios de transmisión se caracterizan por utilizarse en rangos de frecuencia de trabajo diferentes.

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A transmission medium is a material substance (solid, liquid, gas, or plasma) that can propagate energy waves. For example, the transmission medium for sounds is usually air, but solids and liquids may also act as transmission media for sound. The absence of a material medium in vacuum may also constitute a transmission medium for electromagnetic waves such as light and radio waves. While material substance is not required for electromagnetic waves to propagate, such waves are usually affected by the transmission media they pass through, for instance by absorption or by reflection or refraction at the interfaces between media. The term transmission medium also refers to a technical device that employs the material substance to transmit or guide waves. Thus, an optical fiber or a copper cable is a transmission medium. Not only this but also is able to guide the transmission of networks. A transmission medium can be classified as a: \n* Linear medium, if different waves at any particular point in the medium can be superposed; \n* Bounded medium, if it is finite in extent, otherwise unbounded medium; \n* Uniform medium or homogeneous medium, if its physical properties are unchanged at different points; \n* Isotropic medium, if its physical properties are the same in different directions. Electromagnetic radiation can be transmitted through an optical medium, such as optical fiber, or through twisted pair wires, coaxial cable, or dielectric-slab waveguides. It may also pass through any physical material that is transparent to the specific wavelength, such as water, air, glass, or concrete. Sound is, by definition, the vibration of matter, so it requires a physical medium for transmission, as do other kinds of mechanical waves and heat energy. Historically, science incorporated various aether theories to explain the transmission medium. However, it is now known that electromagnetic waves do not require a physical transmission medium, and so can travel through the "vacuum" of free space. Regions of the insulative vacuum can become conductive for electrical conduction through the presence of free electrons, holes, or ions. Transmission and reception of data is performed in four steps. 1. \n* The data is coded as binary numbers at the sender end 2. \n* A carrier signal is modulated as specified by the binary representation of the data 3. \n* At the receiving end, the incoming signal is demodulated into the respective binary numbers 4. \n* Decoding of the binary numbers is performed

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