Magnetic stripe technology is everywhere. We use cards with magnetic stripes on them everyday without even thinking about it. The technology has been with us for many years. The first use of magnetic stripes on cards was in the early 1960’s. London Transit Authority installed a magnetic stripe system in the London Underground (UK).
Magnetic stripes are thin layers of ferrous oxide applied to the surface of a card. Magnetic stripes generally come in two configuations: High Coercivity (hi-co) or Low Coercivity (lo-co). An easy way to tell them apart is that the Hi-Co Stripe is black, and the Lo-Co Stripe is brown.
Coercivity is measured in Oersteds. The Oersted Rating refers to the amount of power you needed to push through a mag head reader so that you can successfully write data onto the magnetic metal stripe. A Hi-Co mag stripe typically carries an Oersted rating of 2750, while some manufacturers offer a 4000 Oersted magnetic stripe. Universities typically opt for 2750 and that seems to be the industry standard. Hotels typically use a low-coercivity stripe, but the stripe is prone to de-magnetize more easily.
Magnetic stripes are available in multiple sizes, the most popular being 1/2" wide containing three-tracks, and a 5/16" wide containing two tracks. Depending upon which track you plan to encode will determine which width you opt for.