Since devices with Bluetooth wireless technology communicate using radio waves, they do not need to be in direct line-of-sight. Bluetooth devices must, however, be within 10 meters (33 feet) of each other, although the connection may be subject to interference from obstructions such as walls or from other electronic devices.
Paired devices can connect to your phone when Bluetooth is switched on. Other devices can detect your phone only if the Bluetooth settings view is open.
Do not pair with or accept connection requests from an unknown device. This helps to protect your phone from harmful content.
The passcode is only used when you connect to something for the first time.