A tag or label (basically a miniature) attached to a product responds to a specific frequency emitted by a transmitter antenna (usually one or two pedestal of the entry/exit gate). The response from the label is then picked up by an adjacent receiver antenna (the other pedestal). This processes the label response signal and will trigger an alarm when it matches specific criteria.
Both the transmitter and receiver are combined in one antenna frame -- these are called mono systems and they can apply pulse.
Mono systems could be effective for you if your store's entry is small.