No power supply required
Light weight for portability
Powerful low frequency sound
Shutter mechanism to provide a choice of signals

The hand crank sirens does not need power supply, and can provide an effective alarm in places without power support. The ideal alarm effect can be achieved by shaking the handle clockwise manually. The sound is strong, powerful, and long in wavelength. The loudness of the alarm sound depends on the shaking speed of the handle. The new hand operated siren has a shutter mechanism in the sound window, which can quickly close the sound window, block the sound, and generate different signals.

http://www.lkrescue.com/