How magnetic cards work, and how magnetic cards work!

Magnetic card principle
     Magnetic stripe cards are made by covering the surface with a layer of plastic or coated with other papers. Their main features are high strength, heat resistance, waterproof and moisture-proofing, and relatively wear-resistant.
    After the magnetic card is covered with this film, the machine writes some magnetic field information into the card. We call these magnetic field particles. These particles are very fine and stored on the membrane on the card's surface. They consist of many different magnetic particles, which provide different information. Then, through the magnetic card reader, the magnetic field particles on the card surface can be read and recognized. By identifying these magnetic particles, the magnetic field information can be output to the computer. This is what people commonly refer to as data displayed after swiping the card.
    Within a magnetic strip, there are three independent tracks, called TK1, TK2, and TK3. TK1 can write up to 79 letters or characters; TK2 can write up to 40 characters; TK3 can write up to 107 characters. Magnetic cards can also be divided into high-resistance and low-resistance stripes. High-resistance stripes are especially resistant to environmental interference, while low-resistance stripes are less resistant to environmental interference. However, there are drawbacks: magnetic stripes have small information storage capacity, are easy to read and forge, and have poor confidentiality, thus requiring support from computer networks or central databases.

How magnetic cards record data
    The recording head consists of an annular iron core with internal gaps and coils wound around the core. Magnetic cards are made from a substrate of a specific material and micro-magnetic materials evenly coated on the base of the magnetic card reader. During recording, the magnetic surface of the magnetic card moves at a certain speed, or the record head moves at a certain speed, contacting the gap or magnetic surface of the recording head. Once current is applied to the coil of the magnetic head, a magnetic field proportional to the current is generated at the gap, so the magnetic material in contact between the magnetic clip and the gap is magnetized. If the current of the recorded signal changes over time, then when the magnetic material on the magnetic card passes through the gap (because the card or magnetic head is moving), it will be magnetized to varying degrees according to the current. After magnetization of the magnetic card, the magnetic layer of the card leaving the gap leaves residual magnetism corresponding to the current change.
    If the current signal (or magnetic field strength) changes according to the sinusoidal pattern, then the remaining magnetic flux on the magnetic card also changes according to the sinusoidal pattern. When the current is positive, it causes a magnetic polarity from left to right (from N to S); When the current reverses, the magnetic polarity also reverses. The final result can be seen as a wavelength on the magnetic card from N to S and back to N, or as two magnetic rods connected by the same polarity. This is a somewhat simplified result; however, it must be remembered that the residual magnetism Br varies sinusoidally. When the signal current is at its maximum, the longitudinal magnetic flux density also reaches its maximum. The recording signal is recorded as residual magnetic residual sinusoidal change and stored on the magnetic card.

Introduction to magnetic card tracks
There are three magnetic tracks on the magnetic strip. Track 1, track 2, and track 3 are read/write tracks, which can be read or written during use.
Track 1 can record numbers (0-9), letters (A-Z), and some other symbols (such as parentheses, separators, etc.), with a maximum of 79 numbers or letters.
Tracks 2 and 3 can only record numbers (0-9). Track 2 can record up to 40 characters, and track 3 can record up to 107 characters.
Magnetic strips are thin layers of material composed of arranged and oriented iron oxide particles (also called pigments). They are tightly bonded with resin adhesives and bonded to non-magnetic substrate media such as paper or plastic.

A brief description of the magnetic card
Essentially, magnetic stripes are the same as tapes or disks used in computers; they can be used to record letters, characters, and numeric information. By bonding or heat-sealing, magnetic cards are firmly integrated with plastic or paper. The information contained in magnetic stripes is generally larger than that of long barcodes. The magnetic strip can be divided into three independent tracks, called TK1, TK2, and TK3. TK1 can write up to 79 letters or characters; TK2 can write up to 40 characters; TK3 can write up to 107 characters. Because magnetic cards are low-cost, easy to use, easy to manage, and have certain security features, their development has received decades of strong support from many world-renowned companies, especially government departments around the world, making magnetic cards widely used and permeating all aspects of daily life.