Pretty sure the old iphone jack works both ways as you can use it to connect a microphone. That's how those stripe card readers work, sending "modem noise" int

Pretty sure the old iphone jack works both ways as you can use it to connect a microphone. That's how those stripe card readers work, sending "modem noise" into the phone: http://www.instructables.com/id/Read-any-magnetic-strip-card-with-a-Square-reader-/ http://www.instructables.com/id/Read-any-magnetic-strip-card...