looppay : Magnetic Secure Transmission (MST)

http://www.looppay.com/faqs/#post-2169

MST technology generates changing magnetic fields over a very short period of time. This is accomplished by putting alternating current through an inductive loop, which can then be received by the magnetic read head of the credit card reader. The signal received from Loop emulates the same magnetic field change as a mag stripe card when swiped across the same read head. Loop works within a 3-inch distance from the read head. The field dissipates rapidly beyond that point, and only exists during a transmission initiated by the user.