Bluetooth has turned our Inspector Gadget fantasies into reality. Cell phones that stream music to the car stereo, open the garage door and call friends hands-free. Fashionable bracelets that vibrate gently to signal an incoming call, stethoscopes that transmit heart and lung readings directly to a laptop and restaurant tables that double as touch-screen menus.
But exactly how does Bluetooth get all of these gadgets to speak the same language? It’s all about radio signals. Every Bluetooth-enabled device is equipped with a tiny radio transceiver mounted on a chip. The transceiver has a range of ten metres (33 feet), within which it can communicate with any other Bluetooth-enabled device.
Bluetooth devices are bundled with software that helps two or more gadgets connect and share data. In all Bluetooth relationships there is a ‘master’ and a ‘slave’. The master device initiates communication by sending out a page. If the slave accepts the connection, it synchronises with the master and the two begin an intricate dance called frequency hopping.
Frequency hopping is a method for sending and receiving packets of data with limited interference and tight security. Bluetooth radios can choose from 79 RF channels. Every time a device sends or receives a packet, it switches to a different channel. The master choreographs the dance and the slave keeps in step.
When two or more Bluetooth devices connect, it’s called a piconet or a personal area network (PAN). A single device can connect with up to seven other devices within the same piconet, and that same device can join several overlapping piconets at the same time, making the options almost limitless, and what will be developed next really is anyone’s guess.
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