System for controlling distance of elements from reference element, e.g. for supervising individuals, has electronic devices with radio transceiver incorporated in garment or accessory and detects separation based on e.g. signal strength

摘要

The system has small sized electronic devices (P1-P4) incorporated into a garment or accessory. Each electronic device provides a unique identification code, and includes a microcontroller, a radio frequency transceiver and an antenna. A base or reference terminal (1), especially a mobile or portable terminal, is connected with the microcontroller, the radio frequency transceiver and the antenna. A keyboard or other an input device is used to enter data in the portable terminal relating to the devices being monitored. Determination that an electronic device has moved outside the designated boundary is based on signal strength, but in other versions may involve measurement of propagation time or use of GPS receivers.