Blue Box

First: If you’re having trouble with this app… be sure to slide the switch on the side of your phone to in-mute it. If your phone (or iPad) is muted, it can’t generate nor decode audio. To the developer: Great UI design. I’m using this in my telephone systems class and it’s great. Thanks for writing such a great app.

I'm really happy and very surprised that this exists. Works very well. Only phone phreaks know what this is really used for, or what it used to be able to be used for.

Back in the late 60's and 70's, when AT&T deployed #5 Crossbar switching systems, Blue Boxes were used to emulate the in-band signaling needed to route long distance telephone calls and "surf" the dark unexplored recesses of the long distance telephone network. #5 Crossbar was phased out and replaced with SS7's "out of band" signaling in the late 70's through early 80's rendering the blue box an impotent artifact of ancient history. Nevertheless, the novelty and folklore of the devices continue to persist. I would have liked to have rated this app 5 stars, but had to deduct 2.5 stars because the app name erroneously lead me to expect a DTMF encoder that actually emulated the tone matrix of a true "Blue Box" on the iPhone. When the author includes the correctly tuned matrix in the app I'll update my rating. There's no longer any applicable reasons not to (and haven't been for almost 3 decades). I also had some difficulty with the decoder and subtracted a half point for failing to buffer the touch tone strings detected by the software to work around the frequency detection / number identification issues. Otherwise, the app does everything else it claims, and the ability to adjust pulse and interval lengths was a nice touch. Please fix the frequency encoder and allow the user to switch between Blue Box DTMF and "standard" DTMF.