There are a myriad of security systems available and made for different purposes though broadly speaking for the majority of users they fall into only a few main categories of detection types:

Optical– cameras 

Perimeter– property access monitoring

Standard Alarm System– typically inside intruder detection using a variety of movement/activity sensors 

(See “Putting it Together“)

Generally there is an associated response system typically sirens, strobes, and now more and more sef-monitored radio alerting with cellular texts and wifi, wifi being the less reliable. A popular emerging response is based on the concept of inhibiting further intruder action such as with a Fog Cannon– highly effective as an non-lethal anti personnel device and prices becoming affordable for many users and can easily be included as part of an alarm system.

Today many are installing a combination of systems to take advantage of better security offered by technology, and the pecking order is changing with Perimeter overtaking internal detection as accurate forewarning is now possible and usually preferable before entry can be gained especially as in many instances home alarms are off when the occupants are in so Perimeter offers a much higher personal security factor and therefore greater peace-of-mind. With accurate perimeter management opportunistic home invasions/burglaries cannot take place.