Alarms are a standard security device used by any serious business or home. Alarms can be self-triggered or automatic, but all are effective at reducing risk and warding off threats. Alarms that are self-triggered are generally carried on the person, producing a loud siren-like noise when the person feels threatened and needs attention. Automatic alarms work by motion sensor, triggering when large, human-like presences are detected while the alarm is set, or when the alarm senses tampering. The fear of an alarm is an effective tool in itself, and 'dummy' alarms are also commonly used to scare off intruders, being highly visible on the side of buildings.
The types of alarm available vary depending on user need. Personal alarms are normally electronic, with the removal of a pin or the press of a button triggering a noise, as with the Key Ring Battery alarm systems. They can also produce noise with gas, as with the Gas Operated Personal Alarm canister. Automatic alarms should be placed in strategic locations. The ezlok Contact Activation alarm triggers when the two sections separate, usually by a door opening. The Sure Standalone Alarm, available at easylocks, attaches to surfaces, like a door or window, and is triggered by harsh vibration.