Patent ID: 7623667

Claim:
An accessory that communicates with an electronic device over a wired communications path that includes an audio connector connected to wires in the wired communications path, comprising: at least one speaker that receives analog audio signals from the electronic device through the wires and the audio connector, wherein the audio connector is connected to the accessory and comprises a four-contact audio plug including a tip contact, two ring contacts, and a sleeve contact; an ultrasonic tone generator that supplies ultrasonic signals to a pair of the wires, wherein the pair of wires includes a microphone wire and a ground wire; a microphone that supplies audio signals to the microphone and ground wires; resistively encoded buttons that gather user input from a user for transmission to the electronic device using the ultrasonic signals; an impedance detector that gathers resistance information from the resistively encoded buttons while at least one of the resistively encoded buttons is being actuated by a user, wherein the resistance information is indicative of the user input; voltage detector and latch circuitry that measures voltages across the microphone and ground wires, wherein the voltage detector and latch circuitry produces an output signal; and switching circuitry that is controlled by the output signal, wherein the switching circuitry comprises switches that may be placed into a first configuration by the output signal when it is desired to operate the accessory in a tone mode in which the ultrasonic signals convey the user input to the electronic device and that may be placed into a second configuration by the output signal when it is desired to operate the accessory in a resistance detection mode in which the electronic device gathers the resistance information from the resistively encoded buttons without using the impedance detector.