How can the computer recognize when a phone that has been paired via Bluetooth is either paired or disconnected?

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The computer can recognize when a phone that has been paired via Bluetooth is either paired or disconnected by constantly monitoring the Bluetooth connection status. When a phone is paired with a computer via Bluetooth, a secure wireless connection is established between the two devices. The computer will constantly monitor the Bluetooth connection and will receive a signal from the phone when it is connected or disconnected from the computer. This signal is transmitted via the Bluetooth protocol and is recognized by the computer's Bluetooth software. When the computer receives the signal that the phone has been disconnected, it will update its Bluetooth connection status accordingly, and may also trigger certain actions, such as closing an application that was running on the phone or shutting down the computer. Conversely, when the phone is connected, the computer will recognize this connection and can take certain actions such as automatically launching a specific application or initiating a file transfer.