Aug/Sept 2007

Zigbee low-power wireless networking technology has been harnessed for a personal tracking system suitable for large sites such as warehouses, factories, hospitals, yards and other extended locations.

The system comes from IDC (Intelligent Distributed Controls), and is simply called the personal interactive tracker system. The company calls it a true 'system-on-a-chip' product.

Two alternative hardware devices are on offer for carrying by the tracked individual. Both are smart keyfob-style units; one has up to five progammable buttons, the other nine. These allow administrative staff to track individuals, and also send messages to and from them. They have 'positional location engines' built into them.

Zigbee works on IEEE wireless standard 802.14.4, which involves very low-power signals that can be powered by long-life batteries. Zigbee devices can be linked into 'wireless personal area networks', or WPANs, communicating with a base station that collects the data and relays it to and from a suitable communication point.

In static applications (for instance, where they are monitoring machine performance or status), the Zigbee transponders can lie in 'sleep' mode for 99 per cent of the time, and be awoken by a beacon signal, or at set time intervals.

Hundreds of such devices can be linked in what the company describes as star, tree and mesh configurations.