Abstract: A frequency scanning radio receiver scans and receives transmissions on discrete radio frequencies. The frequency scanning radio receiver is programmable to monitor frequencies in a geographical area where the receiver is located. The receiver is coupled to a communication device, located externally or internally of the receiver, for communication with a positioning system, such as the global positioning system, to determine the geographical location of the frequency scanning radio receiver either automatically or in response to a manual request. A data base of frequency allocation data, either internal to the radio or in a remotely located host system, provides frequency data to a memory in the frequency scanning radio receiver based on geographical location of the receiver determined through the communication device to program the receiver to monitor local radio frequency transmissions.

Abstract: Detection apparatus for alerting an operator of a moving vehicle to the proximity of a radio transmitter of known frequency and power, typically in a police vehicle. The detection apparatus includes a scanner radio having a selected channel set to the know frequency so that it provides a channel active signal during the time that the police vehicle transmitter is on. The detection apparatus further includes a timing circuit for generating a delay interval representative of the maximum time for the moving vehicle to pass the police vehicle and circuitry for generating a visual and/or audible operator alarm during the channel active signal and during the delay interval. The scanner radio is also utilized to monitor voice transmissions between the dispatcher and the police vehicle, thereby providing the vehicle operator with additional information regarding nearby police vehicles.