final (F) bit, 286-287 framing bits, 116, 122 final routes, 11, 178, 179f free-run accuracy, 140 finite traffic sources, 60 free-space loss (FSL), 204, 205, 226, 463 first-come, first-served queue discipline, 63 calculating, 227 first trial, 58 frequencies. See also frequency 5ESS switch, 136 heterodyning (mixing) of, 80 five-needle telegraph, 20 pilot, 85 fixed-gain devices, 101 frequency, 23 fixed routing scheme, 182 with coaxial cable, 245-246 fixed stuff columns, 491 human voice, 90 flat response, 627, 628f music and, 24 floating mode, 495 radio, 24, 25, 26f flow control, 284, 366-367 sound, 24 Ethernet full-duplex link, 305 frequency assignment, 216 protocol function for, 279-280, 284 frequency bands, satellite communication, 219-220 signaling link layer, 370 frequency-delay response curve, 268, 269f TCP, 326 frequency diversity, 215-216, 466 flux, 586 frequency division duplex, 348 flyback, 407 frequency division multiple access (FDMA), 220, FM broadcast band, 24 FM/fiber hub, 445f advantages and disadvantages of, 222 FM fiber-optic systems, 443-447 digital access by, 228 link performance of, 446f frequency division multiplexers (FDM), 51, 52, focused overload, 550 187. See also FDM entries; wavelength forced updating, 427 division multiplexing (WDM) format identifiers, HDLC, 286 forums, 16 frequency division multiplexing, 79-84 forward-acting error correction (FEC), 256-257. CCITT modulation plan, 81-83 See also forward error correction (FEC) line frequency, 83-84 forward direction signaling, 150 signal mixing, 80-81 forward error correction (FEC), 214, 217 frequency hop, 472 forward explicit congestion notification (FECN) frequency justification, synchronous digital bit, 331, 332, 335, 511 hierarchy, 506-507 forward indicator bit (FIB), 371 frequency modulation (FM), 29, 30f forward sequence number (FSN), 370-371 frequency plans, 216-217 four-wire transmission, 75 subsplit and extended subsplit, 454 fractions, 606 frequency reference exchange, 140 FRAD (frame relay access device), 331, 337 frequency respo