Bluetooth technology is widely used in our daily life, such as Bluetooth headset, Bluetooth bracelet, etc. Bluetooth technology has already connected our life and technology closely.

Bluetooth technology is a short-range wireless communication technology. With the rapid development of the information age, people are using more and more digital devices, which also need to lay more and more cables in the office and home, and Bluetooth technology does not need cables to solve this problem. Bluetooth technology effectively simplifies the communication between various mobile communication terminal devices and is widely used in all areas of our life.

Bluetooth works in the ISM band, which is a worldwide band reserved for industrial, scientific and medical use. Since the ISM band does not require a special license at all, it is used by a wide variety of devices, including Wi-Fi, microwave ovens and car door openers, in addition to Bluetooth. In order to circumvent the problem of congestion, frequency hopping technology is applied to the top of Bluetooth, the use of frequency hopping technology at the same time also enhances the anti-interference ability of Bluetooth technology.

There is a master-slave relationship when two Bluetooth devices are connected, i.e. one is the master device and the other is the slave device, in order to communicate. The master device initiates the pairing, and the slave device will match it separately, and the device with Bluetooth capability can switch freely between the master and slave relationship.

So how do the Bluetooth devices call each other? First of all, the Bluetooth master device initiates the call and will look for all the Bluetooth devices in the vicinity, at this time the slave device must be in the findable state, and the two need to enter the PIN code of the slave device when pairing, but some devices do not need to enter. After the first pairing, the slave Bluetooth device will record the trust information of the master device, and then the master and slave devices can remain in a permanent callable state, and both can initiate a Bluetooth disconnection, and then need to re-pair when they need to call again.

Today's Bluetooth technology not only has a large transmission range, but also has strong penetration capabilities. Frequency hopping technology ensures that it is resistant to interference and is not easily eavesdropped on, making it a promising application.