When Direct Alarms install a wired burglar alarm in your home, it will be connected to your electrical circuit, relying on this to send information back to the central control panel.
When the alarm is triggered by sensors or controls, you will be directly alerted - as well the security company, if that is part of your alarm package.
Whilst there are the newer wireless counterparts, some people prefer the more reliably consistent connection of a wired system, which are less prone to interference, networking issues and false alarms.