Abstract: An apparatus (10, 240, 300) includes a signpost (11, 241-256, 322, 612, 623, 626-628, 652, 661, 682, 686, 703) which transmits signpost signals (24) that are received by a tag (12, 271-275, 301-316, 395-397, 616-618, 641-643, 653, 656-657, 662-664, 679, 708, 711). The tag in turn transmits radio frequency beacon signals (72) which are received by a reader (13, 261, 319, 521-530). The tag can vary the duration of the beacon signals, for example in dependence on whether it is currently receiving a signpost signal. Further, the tag can dynamically vary the transmission rate and/or transmission power of the beacon signals, for example following receipt of a signpost signal. Varying these parameters can facilitate compliance with governmental regulations.

Abstract: An apparatus (10, 240, 300) includes a signpost (11, 241-256, 322, 612, 623, 626-628, 652, 661, 682, 686, 703) which transmits signpost signals (24) to a tag (12, 271-275, 301-316, 395-397, 616-618, 641-643, 653, 656-657, 662-664, 679, 708, 711), which in turn transmits beacon signals (72) to a reader (13, 261, 319, 521-530). One of the signpost and tag is mounted on an item to be tracked. A control system (14, 500) is responsive to the reader, and can cause the signpost to vary the signpost signal in a manner which varies at least one operational characteristic of the tag, such as a transmission rate, a transmission power, a tag identification code, a password, or an encryption code, or which shifts the tag between a normal operational mode and a low power operational mode in which its transmitter is disabled.

Abstract: A signpost (11, 241-256, 322, 612, 623, 626-628, 652, 661, 682, 686, 703) transmits low frequency signals to a beacon tag (12, 271-275, 301-316, 395-397, 616-618, 641-643, 653, 656-657, 662-664, 679, 708, 711), which in turns transmits high frequency signals containing a signpost code from a received signpost signal to a reader (13, 261, 319, 521-530). The signpost can be mounted on one mobile device and the beacon tag on another mobile device, in order to determine when those mobile devices are in close proximity. Further, a sensor (32) can be provided to detect the presence of a mobile device, and to cause the signpost to change the signpost code in its transmitted signals.

Abstract: An apparatus (10, 240, 300) includes a signpost (11, 241-256, 322, 612, 623, 626-628, 652, 661, 682, 686, 703) which transmits signpost signals (24) to a tag (12, 271-275, 301-316, 395-397, 616-618, 641-643, 653, 656-657, 662-664, 679, 708, 711), which in turn transmits beacon signals (72) to a reader (13, 261, 319, 521-530). One of the signpost and tag is mounted on an item to be tracked. A control system (14, 500) is responsive to the reader, and can cause the signpost to vary the signpost signal in a manner which varies at least one operational characteristic of the tag, such as a transmission rate, a transmission power, a tag identification code, a password, or an encryption code, or which shifts the tag between a normal operational mode and a low power operational mode in which its transmitter is disabled.

Abstract: An apparatus (10, 240, 300) includes a signpost (11, 241-256, 322, 612, 623, 626-628, 652, 661, 682, 686, 703) which transmits relatively low frequency signpost signals that are fundamentally magnetic in character, a beacon tag (12, 271-275, 301-316, 395-397, 616-618, 641-643, 653, 656-657, 662-664, 679, 708, 711) which receives the signpost signals and transmits radio frequency signals containing a signpost code (42, 93) from a received signpost signal, and a reader (13, 261, 319, 521-530) which receives the radio frequency signals. One of the signpost and tag is stationarily supported, and the other is mounted on a moveable item. Based on the signals received by the reader, the location of the item can determined with a high degree of accuracy.

Abstract: A signpost (11, 241-256, 322, 612, 623, 626-628, 652, 661, 682, 686, 703) transmits low frequency signals to a beacon tag (12, 271-275, 301-316, 395-397, 616-618, 641-643, 653, 656-657, 662-664, 679, 708, 711), which in turns transmits high frequency signals containing a signpost code from a received signpost signal to a reader (13, 261, 319, 521-530). The signpost can be mounted on one mobile device and the beacon tag on another mobile device, in order to determine when those mobile devices are in close proximity. Further, a sensor (32) can be provided to detect the presence of a mobile device, and to cause the signpost to change the signpost code in its transmitted signals.

Abstract: A security system for monitoring movement of persons in a secured area including set openings which includes area and opening monitors, tag units and an alarm system. The tag unit has special end clamp members which securely clamp an attachment strap to a housing for attaching the unit to a person. Tampering with the connection creates an alarm state. The tag unit includes a dual transmitter continuously transmitting very low frequency (VLF) signal and transmitting a very high frequency (VHF or UHF) signal only if the tag unit is tampered with. The opening monitor includes VLF receivers responsive to a VLF signal and transmitting an alarm signal to an opening alarm system to prevent unauthorized exit. Authorized personnel have a deactivation unit for timed receiver disabling for moving the person through the opening. The UHF transmitter is activated upon unauthorized tampering with the attached tag.