Early security systems involved bells on a door or cans tied to a string that made a loud sound when a door was opened. These were effective until someone figured out how easy they were to remove.
The predecessor of the security systems we know today came about when a clever soul tied a pair of wires to the local police station's alarm panel via telephone lines. Ultimately, this system was updated and they became the norm in households everywhere. Today, wireless security systems are popular, easy to install and don't rely on a hard-wired phone line.