The biggest powered transistor megaphone MG-68 series with with Siren/Whistle functions.
Models: MG-68/MG-68S/MG-68SW(S:siren ,W "whistle)
Power : 45W MAX
Range :0.8~2.2km depending on the oprating conditions
Battery:10x"D"type batteries ,about 20hours for voice,and about 2 hours for signal
External power source :12V battery or 10~13.8V DC