Sensors in IoT devices inform the device about some condition, such as temperature, and forward that information to a controller.

The controller tests the information from the sensor against a collection of possible responses, identifies the appropriate response and then tells the device's actuators to do something, such as send an electrical signal to turn off an appliance.  The device is connected to the network, most often the internet, and communicates and collects data from other devices.

There could be hundreds of sensor-controller-actuator processes in a large system of IoT devices.

There are three main IoT network architectures:

1. Three-layer consists of a perception layer, an application layer, and a network layer. A simple way to think of this architecture is like the human body. The perception layer is like the senses, such as touch, smell and sight. The information the body senses gets sent to the brain, the network, where the information is processed and turned into an action, the application layer.
2. Four-layer adds a specific data processing layer and often act as a security layer.
3. Five-layer adds a processing layer as well as a business layer.

Applications range from consumer electronics to expansive supply-chain programs. One great use case for SIoTDs is supply-chain monitoring and management. For example, smart warehouses.

Warehouse managers can use IoT devices to monitor their inventory levels, which can inform them which inventory items are low or expiring soon.