The compact, lightweight "Heart Alarm" can be attached to your keychain, handbag, clothing, bags, backpacks, or even your school bag using the hook and chain. In an emergency situation, you can easily activate the loud, shrill alarm of approximately 120 dB by pulling on the heart pendant. This pulls the pin on the chain out of the device, triggering the alarm. The heart does not completely detach from the chain; the pin can only be pulled out a short distance. To stop the alarm, simply reinsert the pin back into the alarm. Thanks to the ON-OFF switch (located on the side of the device), the Heart Alarm can be used as a regular keychain both with and without the alarm. Batteries are included; the device is ready to use immediately.