125kHz Card Technology

The first of the proximity technologies was 125kHz.

• When a 125kHz card is powered up, it immediately begins to transmit its card number

  In effect, this is very similar to the way the old mag-stripe readers worked

• The problem is that being a proximity system, it is possible to create a device that will ‘power up’ a card from a distance, then read the data that is being transmitted
• Once you have this, you can easily reproduce the card, making as many copies as you like
• In many cases, you can even create cards in the same series with different numbers