2 ms·
The microphone part of the jack provides a small amount of power to serve as a microphone bias. This can be used to power a few small analog electronics as need
by pclmulqdq 3y ago
The microphone part of the jack provides a small amount of power to serve as a microphone bias. This can be used to power a few small analog electronics as needed. The mag stripe reader may not have needed anything but a reader coil, though, and the phone can probably decode the "sound" that comes from swiping the magnetic stripe.