Patent ID: 8494185

Claim:
An apparatus comprising: an acoustic driver; two audio signal conductors to enable coupling of the apparatus to a device; an audio circuit structured to manipulate an analog audio signal representing a sound provided by the device on the two audio signal conductors to derive a derived sound from the sound, and coupled to the acoustic driver to convey a derived analog audio signal representing the derived sound to the acoustic driver; and a separator circuit coupled to the two audio signal conductors and to the audio circuit, and structured to: employ a first threshold voltage to distinguish between a relatively low DC bias voltage placed across the two audio signal conductors by the device and a first relatively high DC bias voltage placed across the two audio signal conductors by the device; in response to the relatively low DC bias voltage placed across the two audio signal conductors, allow the analog audio signal to be conveyed through the separator circuit from the two audio signal conductors to the audio circuit; and in response to the first relatively high DC bias voltage across the two audio signal conductors, cease to allow an analog signal occurring on one of the two audio signal conductors to be conveyed through the separator circuit to the audio circuit.