transmission medium

Something that passively supports or allows the conveyance or transmission of

a signal, a transmission medium is not necessarily a tangible thing that can be touched.Transmission media can be categorized a number of ways:

• Wired media involve tangible conductors that conduct electromagnetic energy. Metallic conductors support the transmission of electrical energy, with copper, aluminum, and copper-clad aluminum as examples. Metallic conductors are used in twisted-pair (copper) and coaxial cable (aluminum, copper, and copper-clad aluminum) media, for example. Glass and plastic conductors support the transmission of infrared photonic energy in fiber optic networks. See also conductor.

• Wireless media do not involve conductors at all. Actually, “media” is a misnomer, for not only are there no wires, but also there is no physical medium of any sort. Rather, the electromagnetic signal propagates through space between a transmitter and a receiver, with any physical matter (e.g., atomic, molecular, and particulate matter) serving only to attenuate, impede, diffuse, distort, and otherwise interfere with the radio or optical signal.Wireless transmission is synonymous with airwave transmission and includes radio and free space optics (FSO). See also attenuation, diffusion, distortion, FSO, impedance, and radio.

• Guided media incorporate a waveguide, i.e., an enclosed physical structure that contains and guides the signal. Conducted media fit this definition, as insulation and shields variously serve more or less effectively to confine the signal to the conductors and guide it along a physical path. Some radio systems make use of waveguides comprising hollow metal pipes that generally are rectangular, although sometimes circular, in form. Such radio waveguides are restricted to use in very high power or very high frequency applications over short distances, due to their size, weight, and cost.

See also waveguide.

• Bounded media incorporate some form of twisting, shielding, cladding, and/or insulating material that serves to more or less effectively bind the signal within the core medium, thereby improving signal strength over a distance and enhancing the performance of the transmission system in the process.

Twisted pair, coaxial cable, and fiber optic cable fall into this category. See also coaxial cable, fiber optic cable, and twisted pair.

• Class 4/5
• Class 5
• Class A ATM traffic
• Class A cable
• Class A IP address
• Class B ATM traffic
• Class B cable
• Class B IP address
• Class C ATM traffic
• Class C cable
• Class C IP address
• CLASS (Custom Local Access Signaling Services)
• Class D ATM traffic
• Class D ATM traffic
• Class D cable
• Class D IP address
• Class D IP address
• Class E cable
• Class E IP address
• Class F cable
• Classical IP over ATM (Classical Internet Protocol over Asynchronous Transfer Mode)
• Classless Inter-Domain Routing (CIDR)
• class of service (CoS)
• Class X ATM traffic
• clear channel