Circuit/System Description

The rear seat audio (RSA) feature allows rear seat passengers to listen to a different audio program than the front seat passengers. When RSA is on the rear vehicle speakers are muted, and the rear passengers can select their own audio program to listen to using the headphones.

When RSA is turned on, Serial data messaging is used to signal the RSA module to mute the rear speakers.

Each of the audio output channel circuits (+) and (-), at the radio, and at the amplifier (if equipped) have a DC bias voltage that is one half of the battery voltage. When using a DMM, each of the audio output channel circuits will measure approximately 6.5V 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. This voltage will vary depending on what type of audio is being listened to, talk or music, and type of music, as well as the volume setting of the system. Low volume and talk settings will measure around 1V AC and less, where constant music may measure 3V AC and slightly higher. In an amplified audio system, these similar AC voltage measurements may be slightly higher on the output of the amplifier, and the typical AC voltage readings at the output of the radio are less than 1V AC.