73 lines
4.0 KiB
Plaintext
73 lines
4.0 KiB
Plaintext
The Phreaker's Guide to Loop Lines courtesy of the Jolly Roger
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A loop is a wonderous device which the telephone company created as test
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numbers for telephone repairmen when testing equipment. By matching the
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tone of the equipment with the tone of the loop, repairmen can adjust and test
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the settings of their telephone equipment.
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A loop, basically, consists of two different telephone numbers. Let's
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use A and B as an example. Normally if you call A, you will hear a loud
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tone (this is a 1004 hz tone), and if you call B, the line will connect, and
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will be followed by silence.
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This is the format of a loop line. Now, if somebody calls A and someone
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else calls B--Viola!--A and B loop together, and one connection is made.
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Ma Bell did this so repairmen can communicate with each other without
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having to call their own repair office. They can also use them to exchange
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programs, like for ANA or Ringback. Also, many CO's have a "Loop Assignment
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Center". If anyone has any information on these centers please tell me.
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Anyway, that is how a loop is constructed. From this information,
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anyone can find an actual loop line. Going back to the A and B example,
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Note: the tone side and the silent side can be either A or B. Don't be fooled
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if the phone company decides to scramble them around to be cute.
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As you now know, loops come in pairs of numbers. Usually, right after each
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other.
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For example: 817-972-1890
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and
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817-972-1891
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Or, to save space, one loop line can be written as 817-972-1890/1.
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This is not always true. Sometimes, the pattern is in the tens or hundreds,
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and, occaisionally, the numbers are random.
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In cities, usually the phone company has set aside a phone number suffix
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that loops will be used for. Many different prefixes will correspond
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with that one suffix.
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In Arlington, Texas, a popular suffix for loops is 1893 and 1894, and
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a lot of prefixes match with them to make the number.
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For Example: 817-460-1893/4
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817-461-1893/4
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817-465-1893/4
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817-467-1893/4
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817-469-1893/4
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...are all loops...
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or a shorter way to write this is:
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817-xxx-1893/4
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xxx= 460, 461, 465, 467, 469
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Note: You can mix-and-match a popular suffix with other prefixs in a
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city, and almost always find other loops or test numbers.
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Note: For Houston, the loop suffixes are 1499 and 1799. And for Detroit
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it's 9996 and 9997.
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When there are a large number of loops with the same prefix format,
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chances are that many loops will be inter-locked. Using the above example
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of Arlington loops again, (I will write the prefixes to save space) 460, 461,
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and 469 are interlocked loops. This means that only one side can be used at
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a given time. This is because they are all on the same circuit.
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To clarify, if 817-461-1893 is called, 817-460 and 469-1893 cannot be
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called because that circuit is being used. Essentialy, interlocked loops
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are all the same line, but there are a variety of telephone numbers to access
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the line.
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Also, if the operator is asked to break in on a busy loop line he/she
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will say that the circuit is overloaded, or something along those
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lines. This is because Ma Bell has taken the checking equipment off
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the line. However, there are still many rarely used loops which can
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be verfied and can have emergency calls taken on them.
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As you have found out, loops come in many types. Another type of loop is a
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filtered loop. These are loop lines that the tel co has put a filter on, so
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that normal human voices cannot be heard on either line. However, other
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frequencies may be heard. It all depends on what the tel co wants the
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loop to be used for. If a loop has gotten to be very popular with the
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local population or used frequently for conferences, etc. the tel co may filter
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the loop to stop the unwanted "traffic". Usually, the filter will be
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removed after a few months, though.
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----------------Brought to you by the Jolly Roger
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