 maximum number of impedance to ground on one wire is very different from that on packets which can be sent before an acknowledgement is the other wire. necessary. Unipolar. A semiconductor component in which conduction OC- Wink. A single pulse sent between switching systems to indicate curs either due to holes or electrons but not both at the same that they are ready to interchange address data. time. See also bipolar. Wire centre. Generally used to describe any building which houses Up-link. The carrier signal used to transmit information to a one or more large switching system serving several office satellite from the earth. (See down-link.) codes. Normalisation), 22/21 half length dipole, 6/8-9, 17/7 INDEX AGC (Automatic Gain Control), HF, 17/17 FDM pilots, 20/8 horn feeds, 17/10-12, 52/7 microphones, 58/13 impedance and resistance, 17/5 AIIA (Australian Information Industry isotropic, 6/10, 27/4 Compiled by D. Tyler Association), 22/27 microwave line of sight, 17/12 Aircraft, satellite communications, 51/18 mobile communication, 17/6 Alarms, multipoint systems, 52/6 reporting, 61/13 noise, 27/5 A-law broadcast compander, 4/12, 19/21, T1 and PCM-30 TDM, 21/10-11 offset reflector, 17/10 22/4, 37/7, 56/5 Algorithmic complexity, 4/4 pencil beam, 17/3 A/D see ADC Aliasing, prime focus symmetric reflector, 17/8-9 AAL (ATM Adaption Layer), ISDN, digital video, 57/12 quarter length monopole, 6/10 44/16 PAM, 18/14, 19/12 radiation from types of, 17/5-8 AAN (All Area Networking), 56/16 Allocation, frequency see Frequency radiation resistance, 17/5 Absolute delay see Propagation delay assignment, allocation and management radio paging, 45/13 Absorption, ALOHA usage, reception, by ionosphere, 9/5-6 with capture, 13/8 effective capture area, 6/13 light, 7/12 pure, 13/6-7 high gain rod, 6/13 optical fibre loss, 15/11, 53/5-9 queuing theory, 3/3, 3/16 hypothetical isotropic, 6/13 sound, 8/10 reservation, 13/8-10, 13/19 impedance matching, 6/13 AC line signalling, 43/5-7 rural multipoint, 52/10 loop, 6/13 AC power systems s