In home security systems today, one of the most popular is the wireless burglar alarm.
These alarms are convenient to install and use.
They no longer require the wires of older systems, but work using the same general ideas.
Where as older systems had foil strips around windows and switches on doors that sent an alarm anytime the circuit was broken, the newer systems use infrared light as sensors.
Whenever the plane of infrared light is broke, a signal is sent to the alarm company.
By combining infrared sensors with WiFi, systems can be installed with no wires running to doors or windows.
WiFi allows for easily expanding the system to monitor a very large area with no wires connected to the system.
If the area to be protected increases, all you have to do is add more infrared units.
The absence of wires makes it difficult for would be burglars to detect which windows are protected and which ones are not.
This can give further protection as they must then treat all windows as if they have the alarm system installed.
  One of the reasons for the popularity of wireless systems is the ease of installment.
It does not take highly skilled technicians to install these systems.
The instructions are quite simple and given in an installation manuel.
The result is low cost installation for the consumer.
Almost anyone can afford an entry level alarm system and install the system without having to run unsightly cables around their doors and windows.