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.
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.

It's annoying though, 'cause I can't really afford to put a DVD/new stereo system into it (nor do I really want to 'cause of the value of the car). I live with the radio.