A series of radio frequency identification (RFID) systems are delineated. An RFID system comprises an RFID signpost having a transmitter for transmitting signals of a predefined type, and a receiver for receiving signals of the predefined type, wherein the transmitter for transmitting signals of the predefined type cannot transmit until a determination is made that the predefined type of signal is not present at the receiver. Another RFID system comprises an RFID signpost including a transmitter having a continuous power dissipation rating, and a processor for controlling the transmitter such that peak pulse power of a transmission from the transmitter multiplied by its duty cycle does not exceed the continuous power dissipation rating for the transmitter.