Once the system detects an intruder, it's job is to report that detection. It can do this in two ways.
The most basic and lowest level of reporting is a local siren. A siren sounds in the premise or on the outside of the premise. It is loud and meant to attract attention from neighbours or passerby's. Unfortunately we have been exposed to car alarms and sirens so much in our society, that people tend to ignore them or even worse, become angered by the noise. Either way they do nothing. The other concern is that we rely on a neighbour to come running to the scene and potentially put them in a dangerous situation should they come face to face with an intruder. If you are going to utilize a local siren only, then instruct neighbours to call the police, and not toapproach your home or business.
The second way that an alarm system reports intrusion detection is through a monitoring station. The monitoring station is staffed seven days per week 24 hours per day. As a signal comes in, the operators dispatch the appropriate authorities. If it is a fire signal, they send the fire department. If it is a burglary signal they dispatch the police. If it is a medical alert, they dispatch an ambulance. Monitoring stations also alert keyholders when events occur. All activities are logged, including conversations with premise, keyholders and police dispatch officers. Having your system report via a monitoring station is the most effective, and common method.