ng as a 'master' and one device a 'slave' dur- ing the connection. Up to eight active user devices may form an ad-hoc piconet with one device acting as a master and others as slaves (Figure 12.10). The master controls hopping Broadband Telecommunications Technologies and Management Figure 12.10 Bluetooth piconets sequences and clock timing for all slaves. All communications flow through the master and slaves do not communicate directly. Generally any device may act as a master. However, in most present applications the smart phone is the master. In contrast to Wi-Fi devices which mostly use a centralised access point configuration, Bluetooth devices are generally one-to-one master-slave networks. This is useful in applica- tions such as wireless headsets, printing from mobile devices, sharing files between two com- puters and SO on. These work well regardless of whether any other wireless infrastructure such as 3G/4G or Wi-Fi is available. Example 12.2: Tazzle iT A number of Bluetooth devices were developed in response to the need for ad-hoc peer-to-peer communications for file transfer or printing applications in the early 2000s. Most computers and printers were shipped without Bluetooth or Wi-Fi connectivity, and therefore stand-alone PC cards or USB dongles were offered to the market. One such device was Tazzle iT, a Bluetooth dongle which was designed to connect Blackberry smart phones to any PC. Bluetooth equipped Blackberry phones could pair with a Tazzle dongle and send files to computers for printing or sharing. A competitive advantage of Tazzle was that all files transferred from a Blackberry device resided on the dongle and there- Shoot a video fore full security could be ensured. The arrival of iPhones and later on Android smart phones on the market largely eroded the share of Blackberry Personal Wireless Communications Systems devices. Tazzle dongle software has evolved to work with new smart phones Insert the Tazzle iT again to facilitate secure file transfer into PC's USB port where other networking