Medium - This may require entering a PIN code on initial connection to pair the scanner and device. If connecting to a Bluetooth 2.1 or later device, this setting uses the “passkey entry” method for secure and simple pairing.
High - This enables “man in the middle” protection for Bluetooth 2.1 and later. Not all devices support this mode.
Legacy (Bluetooth 2.0 and earlier) - This enables authentication and encryption for legacy pairing.