Magtek InSpec 9000 Manuel d'utilisateur télécharger pdf (Page 79)

Appendix C. Card Standards

HIGH COERCIVITY MAGNETIC MEDIA

The term "Coercivity" refers to the amount of magnetic field strength necessary to change the

direction of the magnetic field lines. In our discussion of magnetic field lines with the iron rod,

we did not discuss the amount of force that the magnetic field lines generate. The amount of

force is referred to as the Magnetic Field Strength. It is the result of the properties of the metal

(in the iron rod) and the amount of electric current that flows through the wire coil that caused

the rod to be magnetized.

Other metals can produce stronger magnetic fields than iron or gamma ferric oxide. Barium (or

Strontium) Ferrite, for example, is a material from which magnetic tape can be constructed that

requires substantially stronger magnetic fields than gamma ferric oxide to create flux transitions.

Barium (or Strontium) ferrite is one of the materials used to construct "High Coercivity"

magnetic stripes for cards.

Basically, magnetic tape whose coercivity is between 250 to 800 Oersted (typically 250 to 600

for ISO 7811-2 compliance) is considered to be "Low Coercivity". (Oersted is the unit of

measure of coercivity). Gamma ferric oxide magnetic media typically measures around 300

Oersted and is the most commonly used low coercivity magnetic stripe material. Barium (or

Strontium) ferrite magnetic media can possess coercivities between 2500 to 5000 Oersted

(typically 2500 to 4000 for ISO 7811-6 compliance), which is the range considered to be "High

Coercivity".

While High Coercivity magnetic tape requires greater magnetic field strength to encode, the

resulting signal amplitude of the flux transitions can be equivalent to the signal amplitude on

Low Coercivity magnetic tape. This is a key point, as it is at the heart of the ISO High

Coercivity standardization efforts. All existing readers that are designed to read ISO Standard

cards will be able to read ISO Standard High Coercivity cards. The difference is in the amount

of magnetic field strength generated by the encode head necessary to properly encode the chosen

magnetic tape coercivity. Since it makes no difference, to ISO compatible readers, what the

coercivity of the magnetic tape is, the Encoded Card Tester is likewise ambivalent to the

coercivity of the magnetic tape.

CARD STANDARDS LISTING

International Standards Organization (ISO) documents are available for purchase though the

American National Standards Institute (ANSI) in New York. Their phone number is: (212) 642-

4900.

The following is a listing:

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Magtek InSpec 9000 Manuel d'utilisateur Page 79