Abstract: In a battery operated IR transmitter having at least one IR LED energized by a source of voltage for passing current during transmission of pulses of data, the IR transmitter includes an energy regulator for maintaining transmission energy through the at least one IR LED substantially constant regardless of fluctuations in the voltage. The current is passed for a time duration that increases as the voltage decreases, the time duration being a function of the voltage so as to maintain the transmission energy substantially constant.

Abstract: In a method and system for effecting bi-directional IR data communication between an object transceiver and a reader, the object transceiver transmits successive data packets to the reader, and upon termination of a transmission of each data packet, opens a time window for receiving a transmission from the reader. The object transceiver is typically one of a plurality of object transceivers each worn by a person to whom a short message is to be transmitted and each having a respective unique ID and being able to effect autonomous transmission to the reader. In such case, each object transceiver transmits for a negligible fraction of its duty cycle thereby reducing a likelihood that two or more object transceivers will try to transmit simultaneously. Alternatively, the same objective can be realized by controlling each object transceiver to have a randomly variable duty cycle.

Abstract: A communication device including an RF transmitter mounted in conjunction with an IR transmitter allowing data to be transmitted by RF as well as by IR. Such a device may be a portable badge worn by moving personnel to transmit IR and RF signals to one of a plurality of second devices each being a fixed reader having an IR and RF receiver, and typically being mounted in a respective enclosed space, such as a room. In use, IR transmissions from the portable device are detected by the IR receiver of the reader in the same room and thus provide an immediate identification of the room (or enclosed space) wherein the portable device is located. On the other hand, if the IR transmitter in the portable device is concealed or for any other reason is not within line-of-sight of the reader in its immediate proximity, then the RF signal transmitted by the RF transmitter in the portable device is detected by the RF receiver in the reader, thereby allowing tracking of the portable device in either eventuality.