Does your Mercedes-Benz model have a factory-fitted speaker in the center console that also plays music signal? Often there is "only" one speaker installed for the emergency assistant, but it does not play any music signal. In this case, there are also no two connection lines in the dashboard, only one line for the emergency assistant. If your Mercedes-Benz only has one line, you will need a corresponding connector plug in addition to the center speaker, which you can obtain from your Mercedes-Benz parts dealer. When purchasing the connector, make sure you have the correct part number as both connectors (reverse polarity emergency assist & music connection signal connector) are available. Likewise, if the center speaker is not standard, you will need to lay a signal wire and you will need a DSP amplifier with channel mixer function (UpMix).