(a) As used in this Code section, the term "antishoplifting or inventory control device" means a mechanism or other device designed and operated for the purpose of detecting the removal of specially marked or tagged merchandise from a mercantile establishment or similar enclosure or from a protected area within such an enclosure.

(b) In the case of a mercantile establishment utilizing an antishoplifting or inventory control device, the automatic activation of the device as a result of a person exiting the establishment or a protected area within the establishment shall constitute reasonable cause for the detention of the person so exiting by the owner or operator of the establishment or by an agent or employee of the owner or operator. Each detention shall be made only in a reasonable manner and only for a reasonable period of time sufficient for any inquiry into the circumstances surrounding the activation of the device.

(c) This Code section shall apply only with respect to mercantile establishments in which a notice has been posted in a clear and visible manner advising patrons of the establishment that an antishoplifting or inventory control device is being utilized in the establishment.