populated segment A network segment that contains end nodes, such as workstations. punch-down block A panel of data receptors into which twisted pair wire is inserted, or punched down, to complete a circuit. radio frequency interference See RFI. Recommended Standard 232 See RS-232. regeneration The process of retransmitting a digital signal. Regeneration, unlike amplification, repeats the pure signal, with none of the noise it has accumulated. registered jack 11 See RJ-11. registered jack 45 See RJ-45. repeater A device used to regenerate a signal. RFI (radio frequency interference) A kind of interference that may be generated by broadcast signals from radio or TV antennas. RG-6 A type of coaxial cable with an impedance of 75 ohms and that contains an 18 AWG core conductor. RG-6 is used for television, satellite, and broadband cable connections. RG-8 A type of coaxial cable characterized by a 50-ohm impedance and a 10 AWG core. RG-8 provided the medium for the first Ethernet networks, which followed the now-obsolete 10BASE-5 standard. RG-58 A type of coaxial cable characterized by a 50-ohm impedance and a 24 AWG core. RG-58 was a popular medium for Ethernet LANs in the 1980s, used for the now-obsolete 10BASE-2 standard. 4
RG-59 A type of coaxial cable characterized by a 75-ohm impedance and a 20 or 22 AWG core, usually made of braided copper. Less expensive but suffering greater attenuation than the more common RG-6 coax, RG-59 is used for relatively short connections. RJ-11 (registered jack 11) The standard connector used with unshielded twisted pair cabling (usually Cat 3 or Level 1) to connect analog telephones. RJ-45 (registered jack 45) The standard connector used with shielded twisted pair and unshielded twisted pair cabling. round-trip time See RTT. RS-232 (Recommended Standard 232) A Physical layer standard for serial communications, as defined by EIA/TIA. RTT (round-trip time) The length of time it takes for a packet to go from sender to receiver, then back from receiver to sender. RTT is usually measured in milliseconds. SC (subscriber connector or standard connector) A connector used with single-mode or multimode fiber-optic cable. serial A style of data transmission in which the pulses that represent bits follow one another along a single transmission line. In other words, they are issued sequentially, not simultaneously. serial cable A cable, such as an RS-232 type, that permits serial data transmission. sheath The outer cover, or jacket, of a cable. shield See braiding. shielded twisted pair See STP. simplex A type of transmission in which signals may travel in only one direction over a medium. single-mode fiber See SMF. SMF (single-mode fiber) A type of fiber-optic cable with a narrow core that carries light pulses along a single path data from one end of the cable to the other end. Data can be transmitted faster and for longer distances on single-mode fiber than on multimode fiber. However, single-mode fiber is more expensive.
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- Category 5 cable, Twisted pair, Coaxial cable, fiber-optic cable