Often times when I reread some of my comments about alarms and alarm systems. I sometimes feel like I bully people with my alarm comments. Of course that is never my intentions.
Over 25 years ago, I hardwired my first alarm system, it was in my first home also. I completely remodeled that home to include solid doors and new windows.. everything had good locks too. I also added outside lighting and landscaped so as to not have hiding places near the home.
The great thing about the alarm was it assured a completed process. Our process before I installed the alarm was close and lock the doors and windows... then leave through the exit door. The door we used normally... when leaving.. locked itself behind us. However... before the alarm was installed it was comman to find particularly open windows and on occasion an open door. Making setting the alarm part of the leaving the house process completely eliminated that.. as alarms generally won't arm with open doors and/or windows.
Alarm systems provide peace of mind too. A noise in the night wakes most people... including me. How often has someone roamed the house at night after hearing something.. to be sure no one had broken in. My brother nearly shot a rattling furnace door one night... many years ago. Having an alarm can mean rolling over and going back to sleep.
My dad was a (high ranking) career policeman. He knew that some neighborhoods were often put at risk of burglary because budget restrictions slowed responce times in those areas. Larger cities provide uniform response times by having "stations" (from where police are dispatched). Dad knew the "bad guys" knew the response times as well as he did. How long it takes for the police to get to any given area adds to or reduces the risk to that area.
I don't expect my alarm to scare-off anyone. I often read that people expect the alarm to scare-off intruders. I am sure some intruders are scared-off by alarms. But I feel the plan to scare someone with a buzzer... might not be well thought out.
It's like steven r and X10 says: "An alarm system also is not a substitute for property owners, renters, or other occupants to act prudently to prevent or minimize the harmful effects of an emergence situation."