Abstract: The invention consists of an apparatus and an operative method with which a transponder is detected and read in a controlled passageway. The detection and reading apparatus is programmed to control its transmitter coil (Tx) so as to repeatedly emit a detecting electromagnetic field only for a brief interval of the transmission signal period, of a sufficient duration to allow the transponder to emit its presence signal. When the detection and reading apparatus receive the transponder's first presence signal, the transmission coil (Tx) is instructed to emit an electromagnetic field of longer duration, sufficient to activate the transponder so that it emits its own complete coded signal so that it can be read and decoded.

Abstract: The present invention provides a detector system for access control, the system comprising: transmitter coils; associated receiver coils; transponders suitable for generating identifiable signatures; and processor circuits adapted firstly to detect a weapon passing between the transmitter and receiver coils by analyzing variations in the signal received by the receiver coil, and secondly to detect the identifiable signature of a transponder on the basis of the signal received by the receiver coils; wherein: the transmitter coils are adapted to generate respective frequencies, firstly for exciting and detecting any weapons passing between the transmitter and receiver coils, and secondly for activating transponders; the transponders have means suitable for powering their internal circuits electrically from the signal received at the "activation" frequency; each weapon excitation and detection frequency is very different from each frequency used for activating transponders and for transponder signatures; and the