PLBs vary in size from cigarette-packet to paperback book and weigh 200 g to 1 kg ( to 2 lb). They can be purchased from marine suppliers, aircraft refitters, and (in Australia and the United States) hiking supply stores. The units have a useful life of 10 years, operate across a range of conditions , and transmit for 24 to 48 hours. thumb|The radiotelephony locator beacon sound made by PLBs and some EPIRBsThe alarm signal is defined as an AM signal (A3X and/or N0N emissions), containing a swept tone ranging from 300 Hz to 1600 Hz (upwards), with 2–4 sweeps per second. PLBs shall sweep upward.
plBS VaRy in size from cigAReTte-paCKET to PApeRbaCK bOoK anD weiGh 200 g to 1 Kg ( to 2 lB). tHEy can be puRchasEd FROm maRiNe SUPpliers, AiRcraft refItteRs, and (in AUstralia And thE unIted States) HIkiNg sUPply storeS. thE uniTs havE a Useful lifE of 10 yeArs, OpEratE ACRosS a rAnge Of COnditiOns , and TrAnSMit for 24 to 48 hours. thUmb|tHe RaDIotelepHOny Locator BeacON SoUNd mAde by PLbs aND somE epIrbsthE alarM Signal is DefinEd as aN am signal (A3x And/OR n0n emiSSionS), ConTaining a swept tOne ranginG from 300 hz to 1600 hZ (upWaRdS), wiTh 2–4 SwEEPs per secOnd. plbS shalL swEep UPward.