Have you ever wanted to just plug your phone / audio device straight into a car radio. Here are the details to connect a 2.5mm audio jack or Bluetooth receiver into a standard car radio. The car is a Ford focus 2003 the radio model is a 6000cd. The pictures below show the solder points. there are 4 points that represent each speaker. So if you had a quadraphonic input source you could have it control each speaker individually. However, I am using a stereo Bluetooth output device so I paired red and white and black and red (thicker) together.

There are 4 connectors solder point inside the radio that will amplify a standard line signal.