Thief alarm systems are one of the best additional security investments you can make to protect your residence from break-ins and other illegal intrusions. Burglar alarm systems may not physically buttress the windows or doors of your home from infiltration by burglars but their security capabilities are however handy in most homes. The main function of a home security alarm is to alert the house owner, as well as others nearby if feasible, if an illegal intrusion of residence is happening. Its second function is to deter the attempting thief from entering the house now that their cover has been blown.