All biometric readers work similarly, by comparing the template stored in memory to the scan obtained during the process of identification. If there is a high enough degree of probability that the template in the memory is compatible with the live scan (the scan belongs to the authorized person), the ID number of that person is sent to a control panel. The control panel then checks the permission level of the user and determines whether access should be allowed. The communication between the reader and the control panel is usually transmitted using the industry standard Wiegand interface. The only exception is the intelligent biometric reader, which does not require any panels and directly controls all door hardware.

The article about this phenomenon in Encyclopædia Britannica places emphasis that "… one by one spiritual mediums were convicted of fraud, sometimes using the tricks borrowed from scenic "magicians" to convince their paranormal abilities". In the article it is also noted that "… the opening of the wide ranging fraud happening on spiritualistic sessions caused serious damage to reputation of the movement of a Spiritualism and in the USA pushed it on the public periphery".[205]

In 1880 the American stage mentalist Washington Irving Bishop published a book revealing how mediums would use secret codes as the trick for their clairvoyant readings.[84] The Seybert Commission was a group of faculty at the University of Pennsylvania who in 1884–1887 exposed fraudulent mediums such as Pierre L. O. A. Keeler and Henry Slade.[85] The Fox sisters confessed to fraud in 1888. Margaret Fox revealed that she and her sister had produced the "spirit" rappings by cracking their toe joints.[86]