2600 hertz: Difference between revisions
Content deleted Content added
Wtshymanski (talk | contribs) suggest merge; context same as blue box. |
Wtshymanski (talk | contribs) redirected |
||
| Line 1: | Line 1: | ||
#REDIRECT [[Blue box]] |
|||
{{Listen|filename=2600 Hz.ogg|title=2600 Hz|description=A tone of 2600 Hz ('''LOUD''')|format=[[Ogg]]}} |
|||
{{mergeto|Blue box|date=September 2011}} |
|||
'''2600 Hz''' is a [[frequency]] in [[hertz]] (cycles per second) that was used by [[AT&T]] as a steady [[Signaling (telecommunication)|signal]] to mark currently unused [[Long distance calling|long-distance]] [[telephone line]]s. |
|||
During the 1960s, [[in-band signaling]] was used, so the same line for both voice [[conversations]] and telephone connection management signals. Since a pause in a voice conversation would produce silence, another method was required for [[telephone exchange|switch]]es to determine available circuits. The solution [[AT&T]] created was to produce a 2600 Hz tone on idling [[Trunking#Telephone_exchange|trunks]]. |
|||
A device, known as a "[[blue box]]", was created to generate the 2600 Hz signal on a line being used. This indicated to switch that the line was idle. After the tone, the switch believed another call was starting, and used the subsequent dialed digits to connect the call.<ref name="sterling">{{cite book |title=[[The Hacker Crackdown]] |first=Bruce |last=Sterling |authorlink=Bruce Sterling |chapter=2 }}</ref> |
|||
This technique only affected interoffice [[multi-frequency]] (MF) trunks; local calls originated and terminated on the same switch. By placing a call to a non-local [[toll-free]] number, interoffice trunks were used for free. Using a blue box would then disconnect the toll-free call and let any other number be dialed. Since the phone was never physically hung up, the connection was still toll-free. |
|||
At one point in the 1960s, packets of the [[Cap'n Crunch]] [[breakfast cereal]] included a free gift: a small whistle that (by coincidence) generated a 2600 Hz tone when one of the whistle's two holes was covered. The [[phreaker]] [[John Draper|Captain Crunch]] adopted his [[nickname]] from this whistle. Others would utilize exotic birds such as canaries which are able to hit the 2600 Hz tone to the same effect. |
|||
In the 1970s and 80s some trunks were modified to filter out [[Single-frequency signaling|SF tone]] arriving from a caller. Later in the 20th century, long-distance companies adopted the [[out-of-band signaling]] system [[Signaling System 7]]. This system separated the voice and signaling [[Channel (communications)|channel]]s, making it impossible to generate these signals from an ordinary phone line. |
|||
==References== |
|||
{{Reflist}} |
|||
==See also== |
|||
*[[Phreaking]], the general term for exploiting the telephone system in unintended ways |
|||
*[[Falsing]] |
|||
*[[Red box (phreaking)]] |
|||
*[[Black box (phreaking)]] |
|||
*[[Blue box (phreaking)]] |
|||
*[[Single-frequency signaling]] |
|||
*''[[2600: The Hacker Quarterly]]'', a magazine named after the 2600 Hz tone. |
|||
{{Telsigs}} |
|||
[[Category:Phreaking]] |
|||
Revision as of 18:31, 7 October 2011
Redirect to: