For another device like a smartphone to use any of the Bluetooth “services” which the micro:bit has, it must first be paired with the micro:bit. Once paired, the other device may connect to the micro:bit and exchange data relating to many of the micro:bit’s features.
Change the output power level of the transmitter to the given value.
bluetooth.setTransmitPower(7);power: a number in the range 0..7, where 0 is the lowest power and 7 is the highest.About Bluetooth, micro:bit Bluetooth profile overview , micro:bit Bluetooth profile reference, Bluetooth on micro:bit resources, Bluetooth SIG