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0002&5 Data ftom many individual remote sites and sensots can ill be transmitted through a single radio frequency in a local area. This is possible because only a minimum amount of information is transmitted; the ID code for the sensor and the raw value of the data. This information can be transmitted in less than 1/4 of a second. Conse- quently, since transmission times are randomly spaced from different sites, the probabilities for interference are extremely small even in dense networks. Even if there is loss of data due to interference, the data is not lost but only delayed because on the next transmission the value transmitted, rainfall for example, indicates a missing count, which is accounted for by the Base Station. Twenty VHF radio frequencies and eight UHF radio frequencies have been assigned for hydro-meteorological data acquisition by the Federal Communications Commission (FCC) in the United States. These frequen- cies' cover the range from 169.425 to 171.925 Mhz and 406.025 to 412.775 Mhz. Other nearby frequencies may also be available for use. For other countries, the HANDAR Synthesized Radio Transmitter covers the range from 150 to 175 Mhz and the UHF radio from 405 to 415 Mhz. In the United States frequencies are used under the sponsorship of a United States Federal agency, such as the National Weather Ser- vice, or any other federal or state agency responsible for acquiring weather or hydrology data. The National Weather Service provides frequency coordination and license assistance through their River Forecast Centers located throughout the United States or rhrough the Office of Hydrology in Silver Springs, Maryland. For additional assistance on the installation and operation of Community Flood Warning Systems, consult the publication, "Guidelines On Community Local Flood Warning and Response Systems" published in August 1985 by the Hydrology Subcommittee of the Federal Interagency Advisory Committee on Water Data. Copies are available from the National Weather Service, Office of Hydrology, Silver Springs, Mary- land. The HANDAR Base Station provides the means to receive the data, collect, store, process, and display it. The Base Station consists of an IBM PC xr with a 20 Megabyte hard disk. HANDAR's Enhanced Alert Software running on a multi-tasking operating system provides a true multi-tasking environment. All reports can be displayed while concu,-=- rently collecting data from remote sites. The HANDAR Enhanced Alert Software provides many functions which are more completely described in this proposal. Among the features included is the ability to display precipitation maps or maps of any other type of sensor with the value of the sensor displayed and up- dated in real-tilne. X-Y graphs can also display, for example, water level or stream flow rate versus time. These graphs can be drawn from a choice of up to sixteen colors. The software also allows setting in alarm limits so that when preset limits for each sensor are exceeded, an alarm action or message is displayed at the base station monitor. The HANDAR Al ert AEWS prov ides many f eatur" of benefi t to the user of the system: 3