Old head units played whatever was in the CD slot or the tape deck, nothing else. Digital media receivers do everything a phone can already do, minus the screen, and route it through actual car speakers instead of a tinny phone speaker fighting road
Posted by nakamichicaraudio 16 days ago (https://servicesdictionary.com/services/do-you-actually-need-a-digital-media-receiver-with-bluetooth-or-just-a-cable)

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