rubee is bidirectional, on-demand, and peer-to-peer. it can operate at other frequencies (e.g. 450 khz) but 131 khz is optimal. rubee tags can have sensors (temperature, humidity, jog), optional displays and may have a full 4 bit microprocessor with static memory. the rubee protocol uses an ip address (internet protocol address). a tag may hold data in its own memory (instead or in addition to having data stored on a server). some tags have as much as 5 kb of memory. rubee functions successfully in harsh environments, with networks of many thousands of tags, and has a range of 1 to 30 m (3 to 100 ft) depending on the antenna configuration. by 'harsh environment' we mean situations in which one or both ends of the communication is near steel or water. rubee radio tags function in environments where other radio tags and rfid may have problems. rubee networks are in use in many visibility applications, including: exit entry detection in high security government facilities, weapons and small arms in high security armories, mission critical specialized tools, smart shelves and racks for high-value assets; smart entry/exit portals.