Way back in the early days of security, there was a thing called a dialer. Some of you readers in my generation might remember the old modems that screeched and hissed when making a connection which was how the security systems communicated with the central station or monitoring center. The monitoring center is the staff of people who watch the information coming in from the security account system and follow the response protocol for specific signals. For example, a smoke sensor signal typically initiates a call to the homeowner and then dispatches the fire department. A door contact or motion would generate a call to the contact numbers you have provided and then dispatch the police. Each device communicates with the security panel, and the panel in turn communicates with the central station. The live operators at the central station give specific instructions on how to respond to the information.
What has changed most today is the adaptation of cellular service. I remember my father-in-law had a fake phone line in clear view of his house with a sign that read “security panel communication line” so that when the bad guy came around with his wire cutters, he would cut the fake phone line instead of the real telephone wire. I thought that was so funny and clever, but thank goodness those days are long gone! There are no longer wires on the outside of the house and most new systems are using a cellular module or communicator instead of the POTS (plain old telephone service). The use of a cellular communicator is a vast improvement for all to the security industry.
It is important when choosing your DIY security to remember that central stations are not all the same. Bigger is not always better, and in fact, bigger is often a problem. The larger the central station, the less personalized and meticulous it will become. You definitely don’t want a bunch of guys in a room taking turns nor do you want a handful of operators setting up shop in some hole in a wall. An mid-sized central station that has been around for 20 plus years and has more than one call center is about right. So, when deciding on your DIY product, make sure to ask a few questions and do your homework. Having something you can depend is worth your time.