Build a Signal Generator with a iPhone

[marzubus]

Yeah I tried that first. but the voltages were much lower -0.1 to +0.1 and the loudpeaker terminals gave me a nice 1v range (-0.5 to +0.5).

And it was more fun to open the sucker up and probe it a little... :D

[lancedulak]

Pretty cool. You could also do this w/o risking yoru phone just write/locate a tone generator program and snip the cable off some cheap earphones.