Alarm systems definitely have a place in a home security plan and are effective, if used properly. The reason why alarms systems deter burglaries is because they increase the potential and fear of being caught and arrested by the police. The deterrent value comes from the Alarm company lawn sign and from the alarm decals on the windows. Home and apartment burglars will usually bypass a property with visible alarm signs and will go to another property without such a sign. Some people, with alarm systems, feel that these signs and decals are unsightly and will not display them. The risk here is that an uninformed burglar might break a window or door and grab a few quick items before the police can respond. Also, don't write your alarm passcode on or near the alarm keypad.