Final answer:
The least expensive exterior IDS sensor is typically the magnetic contact sensor. It consists of two parts: a sensor and a magnet. When the two parts are separated, the sensor sends a signal to the IDS system, triggering an alert.
Step-by-step explanation:
The least expensive exterior IDS (Intrusion Detection System) sensor is typically the magnetic contact sensor. This type of sensor consists of two parts: a sensor and a magnet. When the two parts are separated, such as when a door or window is opened, the sensor sends a signal to the IDS system, triggering an alert. Magnetic contact sensors are commonly used in home security systems and can be purchased at a relatively low cost.
Other types of exterior IDS sensors, such as perimeter motion sensors or infrared sensors, may be more expensive due to the complexity of their technology. These sensors use a variety of methods, such as motion detection or heat sensing, to detect unauthorized entry or movement outside a building.
In summary, the magnetic contact sensor is usually the least expensive exterior IDS sensor, making it an affordable option for home security systems.