I built a redbox back in 96 when I was in highschool, and it worked. If I remember correctly there was only one tiny bit of soldering that had to be made to the

I built a redbox back in 96 when I was in highschool, and it worked. If I remember correctly there was only one tiny bit of soldering that had to be made to the "dialer" which you could buy at any Radioshack. Once the modification was made the button you config'd played a frequency that matched the sound of a quarter. In a lot of older payphones if you put your ear up to the receiver and dropped a quarter in you could actually hear the same sound that the red box generated. A dime / nickle would generate a slightly different tone.