Patent attributes
Aspects of the subject disclosure provide a card reader for receiving payment card information at a mobile point-of-sale terminal. In some implementations, a reader of the subject technology can include a memory, a conditioning module and a 3.5 mm audio plug including an audio bus that is configured for insertion into a headphone port of a host device, such as a smart phone or tablet computer. Implementations of the subject technology also include a microprocessor configured to perform operations for receiving a training sequence for use in determining communication parameters associated with a mobile device, and in response to the training sequence, transmitting an acknowledgement signal to the mobile device, via the audio bus, to indicate that a communicative coupling with the mobile device has been successfully established.
