A system (10) for determining a presence, identity, and duration of presence
in a given area of an object includes one or more mobile transmitters (12)
that periodically send out a beacon signal. A node (14) includes a receiver
(16) that receives a beacon signal whenever a mobile transmitter (12)
is within a threshold range of the node (14). The node (14) includes
a controller (18) that determines a signal strength of each received beacon
signal. The controller (18) compares the signal strength of each received
beacon signal to a reference signal strength associated with the threshold range
in order to determine whether the mobile transmitter (12) was within the
desired detection area of the node (14). A base unit (24) sorts received
information packets for processing by a base computer (28) in order to determine
what mobile transmitter (12) was at what node (14) and for how long.
