While security packages vary between manufacturers, there are some key tools that they all collectively use. Because they all use similar parts, many DIY home security manufacturers offer the option of buying components individually. This allows a user to create a custom home security package, with the components of their choice.
Main Panel with Keypad
Almost all home security systems make use of a main panel of some kind. The main panel and keypad are the brains of a home security system. The keypad is used to activate and deactivate the system. With a more advanced system, you may be able to use it to do things like program alarm settings.
Most security systems include window and door sensors that react when they opened. How many sensors you buy depends on the number of windows and doors in your home, as well as your personal preference.