Abstract: A security tag for deterring theft of an article comprises: an activation sensor; a heating element; a power source configured to supply current to the heating element; and an attachment mechanism configured to secure the security tag to said article. The heating element is arranged to cause a permanent and visible change of state of said article upon application of a current to the heating element either by direct application of heat to said article or by releasing a substance from the security tag onto the article.

Abstract: A security tag for use in a retail environment comprises a main body housing circuitry, the circuitry comprising an oscillator module connected to a buzzer for producing an audible alarm and a switch, and an elongate lanyard extending from the main body and including a normally closed sense loop electrically connected to the circuitry. The switch comprises a transistor. The circuitry is configured such that if the lanyard is cut or otherwise damaged so as to create an open circuit in the sense loop the transistor switch triggers the oscillator module to emit the audible alarm.

Abstract: A method of triggering a security tag attached to an article for deterring theft of said article comprises: emitting a first trigger signal in a first defined area; emitting a second trigger signal in a second defined area, the second trigger signal being different from the first trigger signal; providing a security tag including an activation sensor configured to detect the first and second trigger signals and control circuitry configured to trigger a theft deterrent module of the security tag upon detection of a trigger signal sequence comprising detection of the second trigger signal within a predefined time period after detection of the first trigger signal.

Abstract: A security tag for use in a retail environment comprises a main body housing circuitry, the circuitry comprising an oscillator module connected to a buzzer for producing an audible alarm and a switch, and an elongate lanyard extending from the main body and including a normally closed sense loop electrically connected to the circuitry. The switch comprises a transistor. The circuitry is configured such that if the lanyard is cut or otherwise damaged so as to create an open circuit in the sense loop the transistor switch triggers the oscillator module to emit the audible alarm.