Smartphone / PDA / MP3 music player interface circuit diagrams / circuit schematics
Note that all these links are external and we cannot provide support on the circuits or offer any guarantees to their accuracy.
Some circuits would be illegal to operate in most countries and others are dangerous to construct and should not be attempted by the inexperienced.
If you would like general assistance with a specific design question you may like to try the Electrical Engineering Stack Exchange site below, however please carefully read the help pages before posting:
Electrical Engineering StackExchange