While some psychics utilize Tarot cards to assist them, others rely upon astrology or numerology to help them make predictions and provide guidance. Yet other psychics have a spiritual guide that assists them while others simply have a special sixth sense that allows them to perceive things that others cannot. The method used depends upon the psychic and what he or she needs to do in order to tap into his or her psychic gift.
In the 1-to-many mode a user presents biometric data such as a fingerprint or retina scan and the reader then compares the live scan to all the templates stored in the memory. This method is preferred by most end-users, because it eliminates the need to carry ID cards or use PINs. On the other hand, this method is slower, because the reader may have to perform thousands of comparison operations until it finds the match. An important technical characteristic of a 1-to-many reader is the number of comparisons that can be performed in one second, which is considered the maximum time that users can wait at a door without noticing a delay. Currently most 1-to-many readers are capable of performing 2,000–3,000 matching operations per second.
The difference between the two types of smart cards is the manner with which the microprocessor on the card communicates with the outside world. A contact smart card has eight contact points, which must physically touch the contacts on the reader to convey information between them. Since contact cards must be inserted into readers carefully in the proper orientation, the speed and convenience of such a transaction is not acceptable for most access control applications. The use of contact smart cards as physical access control is limited mostly to parking applications when payment data is stored in card memory, and when the speed of transactions is not as important.
Magnetic stripe technology, usually called mag-stripe, is so named because of the stripe of magnetic oxide tape that is laminated on a card. There are three tracks of data on the magnetic stripe. Typically the data on each of the tracks follows a specific encoding standard, but it is possible to encode any format on any track. A mag-stripe card is cheap compared to other card technologies and is easy to program. The magnetic stripe holds more data than a barcode can in the same space. While a mag-stripe is more difficult to generate than a bar code, the technology for reading and encoding data on a mag-stripe is widespread and easy to acquire. Magnetic stripe technology is also susceptible to misreads, card wear, and data corruption. These cards are also susceptible to some forms of skimming where external devices are placed over the reader to intercept the data read.