Embodiments of the invention include methods, apparatus, systems and means for determining a type of microphone button of a headset plugged into a device jack are described. In some embodiments, a type of microphone button or headset is determined from a plurality of button or headset types based on whether or not a headset plug is detected in a headset jack of a device and whether or not a signal received at a first contact of the headset jack includes overcurrent or an undercurrent.

In some embodiments, the behavior of the device may be controlled based on the type of microphone button or headset determined. For example, a predetermined circuit, a predetermined algorithm, or a predetermined process may be selected to signal process the audio signal of the microphone, based on the type of microphone button or headset. Other embodiments are also described and claimed.

Here's Apple's background and summary of the invention: "Portable devices, such as cell phones, are becoming increasingly common. These portable devices have grown more complex over time, incorporating many features, including, for example, MP3 player capabilities, web browsing capabilities, capabilities of personal digital assistants (PDAs) and the like. Most of these devices include device jacks into which a headset or headphones may be plugged. In some cases, the headsets include earphones for listening to output of the device as well as a microphone to provide input to the device. The headset has a push button to control whether or not the microphone output is sent to the device.

"Methods, apparatus, systems and means for determining a type of microphone button of a headset plugged into a device jack are described. In some embodiments, the type of a given microphone button (or type of headset) is selected (e.g., identified or determined) from several predefined button types (or headset types), based on whether or not a headset plug is detected in a headset jack of a device and whether or not a signal received at a first contact of the headset jack includes overcurrent or an undercurrent (e.g., when the button is pressed, or not in its normal position). The behavior of the device may be controlled (or changed) based on the determined type of microphone button. For example, a predetermined circuit, a predetermined algorithm, or a predetermined process may be selected to process the audio signal of the microphone, based on the type of microphone button. Also, for example, a change may be made from one member to another members of a set of predetermined circuits, predetermined algorithms, or predetermined processes to process the audio signal of the microphone, based on the type of microphone button.

"In some embodiments, the voltage of the signal (at a contact of the headset jack, such as at the first contact) may be compared with an upper voltage threshold and a lower voltage threshold, so that the undercurrent is detected if the voltage of the signal is greater than the upper voltage threshold and the overcurrent is detected if the voltage of the signal is below the lower voltage threshold. The type of microphone button may be a button associated with a normally open switch, if the first signal is detected to be an overcurrent, and with a normally closed switch if the first signal is detected to be an undercurrent. Thus, a type of the headset may be determined based on the type of microphone button (e.g. when the button is pressed) as follows: (1) if the signal is undercurrent, the a microphone button switches between (a) coupling the microphone and (b) coupling an open circuit, to a contact of the plug, or (2) if the signal an overcurrent, the microphone button switches between (a) coupling the microphone and (b) coupling a short circuit to a contact of the plug."

The inventors are Achim Pantfoerder, Twisleton-Wykham-Fiennes and Barnabas Hugo.