Circuit/System Description

The telematics communication interface control module utilizes the vehicles infotainment systems speaker to broadcast audio in the case of emergency road assistance. In the event the infotainment system becomes inoperable there is an emergency backup speaker connected directly to the telematics communication interface control module. Each of the audio output channel circuits (+) and (-), at the telematics communication interface control module have a DC bias voltage that is approximately one half of battery voltage. When using a DMM, each of the audio output channel circuits will measure approximately 6.5 V DC. The audio being played on the system is produced by a varying AC voltage that is centered around the DC bias voltage on the same circuit. The AC voltage is what causes the speaker cone to move and produce sound. The frequency (Hz) of the AC voltage signal is directly related to the frequency of the input. Both the DC bias voltage and the AC voltage signals are needed for the system to properly produce sound.