Bluetooth devices communicate with each other in a piconet, consisting of one master device and between one and seven active slave devices. There may also be up to 255 parked slave devices, which are not communicating at this moment in time.

A master Bluetooth device discovers which other devices are within range using an inquiry procedure. It can then connect to a slave device using by paging it.

A scatternet consists of two or more overlapping piconets. A master in one piconet can be a slave in another, if the other piconet's master pages it (i.e. connects to it).

Device address

Every Bluetooth device has a unique 48-bit BD_ADDR (Bluetooth Device Address), which is divided into three fields:

most significant
NAP (Non-significant Address Part), 16 bits. } These 24-bits are the manufacturer's company_id / OUI (Organizationally Unique Identifier), allocated by the IEEE. For example, Rohde & Schwarz's is 0x0090B8.
UAP (Upper Address Part), 8 bits.
LAP (Lower Address Part), 24 bits. These 24-bits are a serial number assigned by the manufacturer.
least significant

More information

Physical interface
Baseband packets
ACL links
SCO links
eSCO links