MAC frame, 301-304 links, 197 token ring and FDDI, 306-308 fiber-optic, 35, 36f, 233f LAN bridges, 309-310 in long-distance network design, 174-175 land-line Morse code, 22 line-of-sight microwave, 197 LAN segmentation, 310 overbuilding, 214 LAN-to-WAN-to-LAN connectivities, 320f satellite to earth, 219 LAN transmission techniques, 292 virtual channel, 528 LAPB (link access protocol, B-channel), 315 LAPD (link access protocol, D-channel), 315, virtual path, 528-529 329-330 link set, 362 core functions, 330-331 link status signal unit (LSSU), 370, 372, 372 laser diode (LD), 236, 237 "listen before transmit" concept, 300 last-come, first-served queue discipline, 63 LLC data field, MAC frame, 302. See also logical LATA (local access and transport area), 16, 176 link control (LLC) connections, 193 LLC header, 320 latching, 72 load coil spacing (distance), 100, 102-103 laws of logarithms, 612-613 load coil spacing code, 98 laws of signs, 605 loaded cables, 97-98 layering loaded loops, attenuation (loss) of, 98 ATM, 521- -526 loading SS No. 7, 364-374 inductive, 101, 102-103 leading register concept, 160-161 subscriber loop, 97-98 least common denominator (LCD), 606 load sharing, 185. See also signaling link selection LEC (local exchange carrier), 16 (SLS) field length field, MAC frame, 302 local access and transport areas (LATAs), 16, 176, length indicator (LI), 371 level (signal magnitude), 51-52 local area connectivity, tandem switches in, 7 level-regulating pilots, 85 local area networks (LANs), 3, 291-313. See also level settings, CATV amplifier, 439 LAN entries; local networks light detectors, 237-239 access protocols, 298-308 light-emitting diode (LED), 233, 236, 237, 243 ANSI/IEEE protocols, 295-298 limited availability switching, 59 applications, 292 linear equations, 607-608 baseband LAN transmission, 294-295 simultaneous, 610-611 communication channels for, 548 linear predictive vocoders, 468 defined, 291 line build-out (LBO), 103, 121 interworking via spanning devices, 308-312 networks with, 103 topologies,