In some embodiments, a method is provided for identifying a communication interface of an electronic unit attached to a connector of an electronic device. A voltage pulse is generated in the device on a pin of the connector. The voltage on the pin is measured, as it is affected by a load in the unit....http://www.google.de/patents/US7565458?utm_source=gb-gplus-sharePatent US7565458 - Cell phone accessory identification algorithm by generating and measuring a voltage pulse through a pin interface
