The Bluetooth® SIG has defined a full set of profiles that ensures that any device carrying the Bluetooth label will be able to communicate with any other Bluetooth certified device. This type of defined interoperability is not always found with other wireless technologies. Profiles are designed to define a specific application or use-case. In order for two devices to communicate with one another, they need to speak the same language, which is a profile. As shown in this slide, in the picture on the left, a person can use a cell phone through the car speakers, both the cell phone and car are able to connect via Bluetooth because they both support the Hands Free Profile. In the right-hand picture on the slide, the cell phone and the car can not connect because only the car supports the Hands Free Profile. The profiles are positioned on the top of the Bluetooth stack. Developers can add profiles or applications without changing the underlying hardware of the product.