I found an interesting "feature" in the Samsung Indulge's audio jack. My car has a combo CD/cassette player and I've used MP3-cassette adapters in the past with various phones. This permits me to use the phone as an MP3 player in the car, and when I receive calls the audio plays through my car's speakers. (The phone's built-in microphone is used for my audio). With the Indulge (not sure whether or not this also applies to other phones) make sure that you use an MP3-cassette adapter that has a standard 3 conductor stereo (TRS) plug, NOT a 4 conductor (TRRS) plug. The four conductor plug will deactivate the Indulge's microphone and you will only be able to hear the person you're talking to; your end will be muted. Here's an illustration showing the differences between TS (mono), TRS (stereo), and TRRS (stereo plus microphone) plugs.