Originally Posted by dE.fUsEd
old school payphones...you could record the sound of the coins being deposited, then play that sound into a payphone and get free calls.
Or build a box to do it yourself. They called them "red boxes," which were strictly tone generators. Not to be confused with "blue boxes," which were built by Steve Jobs and Steve Wozniak waaaay back in the day. Blue boxes could do a lot more, as I understand it, than just get free calls.
Modern pay phones mute the mouthpiece until the call is connected. No more teh redb0xoring, with some exceptions.