and bridging to other networks. It has the authority to establish networks and perform any network management that might be required. The coordi- nator also has routing capability and may serve as a gateway to the Internet or to other networks, and it can store information about the network. Because it contains the most memory, it is the most expensive of the three devices in a ZigBee network. A ZigBee network is capable of supporting up to 254 FFDs, 1 coordinator, and potentially thousands of RFDs. Most importantly, because the ZigBee protocol expects most messages to receive acknowledgments in order to verify successful reception, all devices are transceivers (i.e., they transmit and receive). Figure 15.7 shows an example of a ZigBee home network. ZigBee devices operate in unlicensed spectrum worldwide and are based on DSSS technology. They operate at the maximum data rates shown in Table 15.8, and their transmission range is 30 to 250 feet (10 to 75 m). The ZigBee standard is designed to provide reliable data transmission of mod- est amounts of data up to 250 feet (75 m) while consuming very little power. It also Door Entry (RFD) Access Motion Control Control Sensor (RFD) Temperature Sensor (RFD) Coordinator Air Conditioner Control (RFD) Central Control Smoke Detectors Point (RFD) Detection Figure 15.7 An example of a ZigBee home network WPANs Table 15.8 ZigBee Maximum Data Rates Number of Location Data Rate Bandwidth Channels Supported Worldwide 250Kbps 2.4GHz The Americas 40Kbps 915MHz Europe 20Kbps 868MHz offers support for critical-latency devices, such as joysticks. ZigBee offers lower power consumption, lower cost, higher density of nodes per network, and simplic- ity of protocols compared with other wireless connectivity schemes. Because ZigBee's topology allows as many as 254 nodes per network, it is ideal for industrial appli- cations. ZigBee is the only standards-based technology designed to address the unique needs of low-cost, low-power, wireless sensor networks for remote moni- toring, home contro