Cassette Adapters

The cassette adapter was invented to allow one to play music through sound systems with a tape player but no auxiliary input. It consists of a 'dummy' tape that contains a tape head in the place where the tape player normally reads the tape. more...

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The head is then connected to a wire going out the side of the tape enclosure which usually has a male Jack plug on the end.

This can then be plugged into a portable audio player such as a Minidisc, CD or MP3 player. This is useful in older cars without CD changers, as many vehicles sold have a cassette player but no facility to play back these other formats. One can use their current device with the cassette deck, negating the need to purchase another digital audio player.

Read more at Wikipedia.org