06. What is a Blue Box? Blue boxes use a 2600hz tone to size control of telephone switches that use in-band signalling. The caller may then access special switch functions, with the usual purpose of making free long distance phone calls, using the tones provided by the Blue Box. 07. Do Blue Boxes still work? Blue Boxes still work in areas using in band signalling. Modern phone switches use out of band signalling. Nothing you send over the voice portion of bandwidth can control the switch. If you are in an area served by a switch using out of band signalling, you can still blue box by calling through an area served by older in-band equipment.