Slaves have to synchronize by the system clock of the master and follow the hopping pattern, determined by the master. Besides, each device can belong to several piconets simultaneously, as they enter radio proximity of other master devices. The main attractive characteristic of Bluetooth is to allow a wide range of Bluetooth enabled devices to connect and communicate with each other, almost everywhere in the world. Another key feature is the ability of devices to communicate without need of line-of-sight positioning of connected devices.