WITH THE ADVENT OF COMPACT EQUIPMENT, SENSITIVE RECEIVERS, AND OTHER COMPONENTS OF MODERN TECHNOLOGY, POLICE RADIO COMMUNICATIONS HAVE CHANGED DRAMATICALLY. GEOGRAPHY IS PROBABLY THE MOST IMPORTANT FACTOR IN DICTATING CHOICE OF EQUIPMENT. THE REGIONAL COVERAGE OF THE HIGHWAY PATORL FREQUENTLY RELIES ON LOW BAND FREQUENCIES, FOR EXAMPLE, WHILE ULTRA HIGH FREQUENCY (UHF) EQUIPMENT IS OFTEN USED IN METROPOLITAN AREAS. MORE EQUIPMENT IS AVAILABLE FOR VERY HIGH FREQUENCY (VHF) HIGH BAND THAN ANY OTHER FREQUENCY RANGE. COMMUNICATIONS EQUIPMENT SHOULD BE FULLY WARRANTED AND SHOULD PROVIDE SATISFACTORY SERVICE. BASE STATION ANTENNAS, MOBILE TRANSCEIVERS, MOBILE ANTENNAS, AND HAND-HELD PORTABLES CAN EXPAND THE VERSATILITY OF POLICE COMMUNICATIONS EQUIPMENT. REPEATERS CAN BE USED TO AMPLIFY AND REBROADCAST WEAKLY RECEIVED SIGNALS, AND VOICE PROTECTION SYSTEMS CAN EXCLUDE UNINVITED LISTENERS. OTHER INNOVATIONS INCLUDE SELECTIVE CALLING OR PAGING SYSTEMS, ELECTRONIC SURVEILLANCE, EQUIPMENT FOR SPECIAL ENVIRONMENTS, AND AUTOMATIC SIGNALING DEVICES. PHOTOGRAPHS ARE INCLUDED. (AOP)