'''Busy line interrupt''', also known as '''emergency breakthrough''', is a function onof telephone [[land line]] telephonescarriers thatin allowswhich a caller[[Switchboard tooperator|telephone interruptoperator]], by request of a caller, interrupts an existing phone conversation ofbetween anotherother caller,parties.<ref>[http://www.icc.illinois.gov/downloads/public/edocket/115077.pdf INWARD ASSISTANCE OPERATOR SERVICES]</ref> especially one who does not have [[call waiting]].
This is especially useful for services without [[call waiting]].
Much like [[long distance]] calling]] before the late 90s1990s, busy line interrupt is a service provided, for instance, to allow people to contact a family member in the event of an emergency if the receiving party's line is busy and the news cannot wait.
The service is not free. It is usually about $3 per use<ref>[http://www.coxbusiness.com/products/voice/basicpricing/clevelandpricing.html Cox Cleveland Pricing]</ref> and is charged whether or not the calling party can reach the person on the other end (as the phone just might be off the hook for privacy reasons or the line mightcould be connectedbusy tocarrying thea [[internet]]modem call). For this reason, it is usually only used in cases of emergency'semergencies as noted above.
In the early 1990's, reports were surfacing that "[[phone phreak]]ers" were having success in manipulating the line interruption function with signaling tones and equipment that emulated the telephone operator's. It was claimed to be possible to eavesdrop on any engaged telephone line by number.
==References==
Line 11 ⟶ 10:
==External links==
*[https://web.archive.org/web/20110612184515/http://www.patentstorm.us/patents/7133515/description.html US Patent 7133515 - Subscriber control of busy line interrupt and line treatment codes]
