Personal alarms
A personal alarm fits in the palm of your hand: an ABS or polycarbonate casing 6 to 9 cm long and weighing 20 to 60 g, typically fitted with a keyring or a carabiner. The piezoelectric transducer delivers a sound level of 100 to 140 decibels depending on the model, measured at one meter. Some casings add a white LED or a strobe flash powered by the same circuit.
Activation, power supply, and maintenance
Two mechanisms coexist: the pin attached to the body by a cord, pulled out with a single tug, and the press-and-hold push button. Power is supplied by LR44 button cell batteries, a CR2032 lithium battery, or a 9 V battery on the loudest models; battery life is expressed in tens of minutes of continuous sound. The choice depends on the stated decibel rating, access to the battery compartment, and the attachment method: ring, clip, or neck lanyard. A quarterly test and replacing spent batteries are all the maintenance required. These units complement other personal defense equipment.
