The PPS23W is a dual function emergency attack alarm. It features a 130 dB alarm, which is the loudest personal alarm sold by Vigilant. It is also the only alarm sold by Vigilant to include a backup feature - it has a security screamer whistle built into the end of the alarm that serves as an emergency backup alert mechanism in the event of battery failure. The alarm is activated by depressing the button on the front of the alarm, but a different button on the back of the unit is the only way to deactivate and silence the alarm. In situations where seconds make a difference between life and death - the ease of activation combined with the "hidden" off button make this alarm an easy to use, and hard to defeat personal alarm. Personal alarms are one of the fastest growin more »