Alarm systems are used to monitor by professional monitoring companies for a monthly fee. There are several type Alarm security system are used for safty like door sensor, glass-break monitor, smoke alarm, motion detector or carbon-monoxide detector--are triggered, a call immediately goes to the monitoring company. The company will subsequently call you as well as the local authorities. This ensures quick response even if you are incapacitated.
Most people who buy an alarm system receive a yard sign from the company that sold them the system. These signs are beneficial to the companies because it essentially is an advertisement for them. It benefits also home or business owners because a would-be intruder is much less likely to attempt to get into a home if he knows there is an alarm in it. Just having the yard sign is a big part of deterring crime with an alarm system.