Talk:Ringback number
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Additional information on special phone numbers
editThe following information is not reliably sourced, but is interesting:
Ringback numbers that produced as a side effect another dialtone instead of a tone and a connected circuit seem to have been discontinued or changed from a short code to a regular-length number at a distinct point in time.[1]
| “ | In most instances you must call the ringback number, quickly hang up the phone for just a short moment and then let up on the switch, you will then go back off hook and hear a different tone. You may then hang up. You will be called back seconds later.[2] | ” |
A current loop is a low-impedance DC circuit (frequently powered at 24 volts) that carries audio as amplitude modulation. A loop, though, is a test number used by telco employees:
| “ | Loops are a pair of phone numbers, usually consecutive, like 836-9998 and 836-9999...When BOTH ends are called, the people that called each end can talk through the loop.[3] | ” |
A dead battery is a now-obsolete special calling number that would connect to a normal DC-powered circuit with no modulation.[citation needed] I'm not sure they exist anymore.
There used to be numbers that would give you a connected line with an audio tone. They were used instead of tone generators or electrical buzzers to trace lines from the street to a house or within a house.[citation needed]
There are some numbers that always answer as busy.[4]
There are some numbers that temporarily disconnect phone service.[5]
Section References
editThe above references were added on March 18, 2010. When checked on April 21, 2020, they were all dead links.--Thomprod (talk) 12:27, 21 April 2020 (UTC)