Most security systems give you the option of self-monitoring or professional monitoring, and you should know your options and the associated costs before you sign a contract. Even self-monitoring systems sometimes charge a small monthly or annual fee. Professional monitoring is more expensive and requires a monthly fee, but you get 24/7 monitoring — the extra cost could be worth the peace of mind you receive.

Older systems used the home telephone line. The old copper-based telephone network was quite reliable and nearly always worked, even during power failures. The major weakness was that it was often easy for a burglar to find the telephone line running into a home and cut it, disabling the phone and the alarm.

Except for older systems that still use the copper-based telephone network, there are two primary ways a system communicates with the monitoring station: a cellular communications network or your home’s Wi-Fi system, which relies on your internet connection.

If you pay for professional monitoring, you’re counting on a team of responders who are available 24/7. When a sensor goes off, you want to know how long the company will take to send you a notification or alert emergency services. Ideally, this is done in less than a minute — in situations like these, every second counts. If the company can’t guarantee this response time, you may want to look elsewhere.

Even the best equipment needs maintenance at some point, and you need to know whose responsibility that is when it happens. Make sure you ask what kind of warranty the equipment is under and what your costs will be after the warranty period is over.

Note that there might be different warranties given by the equipment manufacturer and the company you buy the equipment from. It’s also worth asking how long you’ll have to wait before a technician addresses a warranty concern. This should typically be done within a day or two of the malfunction.