Red box (phreaking)

A red box is a phreaking device that generates tones to simulate inserting coins in pay phones, thus fooling the system into completing free calls.

Commonly used devices include modified Radio Shack tone dialers, personal MP3 players, and audio-recording greeting cards.

However, since ACTS has been phased out of service in much of the United States, combined with the integration of acoustic filters into many payphone handsets, the practice of red boxing is rarely possible any longer.

Canada formerly used a US-style ACTS coin phone system with a tone pair which would beep once for a nickel, twice for a dime and five times on receiving a quarter.

Manipulating a telephone in this way was illegal and carried the specific offence of "abstracting electricity" from the GPO (later the Post Office and later still BT.)