Blue box

A blue box is an electronic device that generates the in-band signaling audio tones used to control local & long-distance telephone exchanges. By generating the same tones employed by a telephone operator's dialing console, a blue box user can route their own calls and bypass the normal toll collection by the telephone company. Developed in the 1960s, the most typical use of a blue box is to place free long-distance telephone calls. A related device, the black box, enabled one to receive calls which were free to the caller. While the blue box still works in some areas in the United States and other countries where some legacy equipment is still in service, most modern switching systems no longer use in-band signaling. Instead, signaling occurs on an out-of-band channel that cannot be accessed from the line the caller is using, a system called Common Channel Interoffice Signaling or CCIS.I called only to explore the phone company as a system, to learn the codes and tricks. I'd talk to the London operator, and convince her I was a New York operator. When I called my parents and my friends, I paid. After six months I quit—I'd done everything that I could.The rightmost column is not present onconsumer telephones. A blue box is an electronic device that generates the in-band signaling audio tones used to control local & long-distance telephone exchanges. By generating the same tones employed by a telephone operator's dialing console, a blue box user can route their own calls and bypass the normal toll collection by the telephone company. Developed in the 1960s, the most typical use of a blue box is to place free long-distance telephone calls. A related device, the black box, enabled one to receive calls which were free to the caller. While the blue box still works in some areas in the United States and other countries where some legacy equipment is still in service, most modern switching systems no longer use in-band signaling. Instead, signaling occurs on an out-of-band channel that cannot be accessed from the line the caller is using, a system called Common Channel Interoffice Signaling or CCIS. In November 1954, the Bell System Technical Journal published an article entitled 'In-Band Single-Frequency Signaling', which described the process used for routing telephone calls over trunk lines with the then-current signaling system, R1. The article described the basics of the inter-office trunking system and the signals used to start, route, and end calls. In November 1960, further technical details were disclosed by the Bell System Technical Journal in an article entitled 'Signaling Systems for Control of Telephone Switching'. This article identified the specific SF (single frequency) and MF (multi-frequency) tones used to start and end a call, and to transmit the called number, on a long-distance connection.