A drive force transmission apparatus disposed within a differential carrier and adapted to drivingly couple first and second rotary shafts. The processing circuit detects a difference in magnitude between output values of the Hall effect devices, as position outputs, with an input value to each of the Hall effect devices being controlled such that a sum of magnitudes of respective output values of the Hall effect devices is constant. The method can include initializing a chat session in an instant messenger, engaging in an audio conversation through the instant messenger, collecting emotion meta-data for the audio conversation and mapping the emotion meta-data to emoticons, and combining a speech recognized form of the audio conversation with the emoticons and text from the chat session into a chat transcript.