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• Power Flux Density-The degree of con- Association for the Advancemeru of Medical centration of radio signal power(such as one Instrumentation. rrucroa.art) in a given unit of area(such as Spectrum-The full range of frequencies one square centimeter). occupied by radio waves,infrared waves, Preamplifier-An electronic component visible light, ultraviolet,X,and gamma rays. which boosts the strength of low-level input signals. In audio systems,a preamplifier TDMA-A means of transmitting more strengthens the weak output signal from a than one signal over a givencommunications magnetic phonograph cartridge to a level circuit by breaking up ecirhinal into a usable by a power amplifier. series of sequential samples,assigning a particular"window"in pine to each signal, Preclusion-Prevention; in radio contexts, and then sequentially transmitting the the prevention of the use of a given frequency samples of different signalsin.their assigned or frequencies in a given area due to the use time windows; also called time division of the same or adjacent frequencies by others. multiplexing(TDM). Short far Tune Division Multiple Access. Range-The geographic area within which a radio system provides effective coverage. Telephone Switching Equipment- Radio Fre quer y-A well above Electromechanical or electronic equipment "� for the routing of telephone calls. the range of human hearing.Abbreviated as RF. Thermal Exposure-Exposure to radio- eceiver-An electronic device which fray potver at levels which cause measurable warming of biological tissue. converts radio-frequency currents into audio or video programming or electronic data. Time Division Multiple Access-See TDMA. Resonance-A condition in which an elec- tronic circuit responds strongly to a particular Transmitter-An electronic device which frequency. converts power frvrvt a battery or the electric Resonant-A circuitdisplayi utility into radio-frequency current for the ng ' purpose of serving information via radio tone of resonance,or the frequency at which waves. a circuit displays such symptoms. UHF-Ultra High Frequency; the part of RF-See Radio Frequency. the radio spectrum in which UHF television Selectivity-The ability of a receiver to stations operate. The FCC has converted ignore signals on frequencies above and scrne UHF TV channels mea frequency below the channel to which the receiver is bands for cellular telephone systems. Ultra tuned. high frequencies lie above very high frequen- cies(VHF),and are deemed part of the Shielding-The use of a particular material microwave region of the spec rum. to shield an electronic component or circuit from the effects of external electric or VHF-Very High Frequency; the par t of the magnetic fields. radio spectrum in which VHF television stations operate. Very high frequencies lie Signal Strength-The amount of power above very ultra frequencies(UHF). ipiontained in an intercepted radio wave. Vot-The fundamental unit of electrical ..xoctety of Biomedical Equipment pressure or electromotive force. Technicians -A professional association of the operators of biomedical electronic equip- Watt'The fiordantental Unit of electrical 40 mom'and an ancillary group of the power,equal to one volt times one ampere.