Direct Access Test Units (DATUs) are special
PSTN
The public switched telephone network (PSTN) provides infrastructure and services for public telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other el ...
phone numbers that terminate at the
central office switch
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type ...
in a telephone company's local exchange that provide switchmen and telco technicians with a circuit for testing lines in various ways.
Among the many things a DATU can do are:
* Make certain electrical connections, such as shorting a line's tip to ring, tip to ground, or ring to ground.
* Play certain tones on the line (high tone, low tone) to test the line's audio circuit.
* Monitor the audio circuit on the line if it is in use (though this only provides a scrambled rendition of the line's audio circuit for privacy and security reasons).
* Create and modify certain variables such as counters and timers on the CO switch, as well as adding and modifying exchanges.
* Remove a line from
permanent signal
Permanent signal (PS) in American telephony terminology, or permanent loop in British usage, is a condition in which a POTS line is off-hook without connection for an extended period of time.Telcordia Technologies, GR-505-CORE Issue 2, December 20 ...
holding state.
DATU's are primarily non-published numbers, though they usually have the phone number XXX-9935 (where XXX represents the local exchange). They are password protected for security, though many telcos leave the
default password of 1111 set.
In July 2004,
New York City
New York, often called New York City or NYC, is the most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the most densely populated major city in the U ...
phone phreak
Phreaking is a slang term coined to describe the activity of a culture of people who study, experiment with, or explore telecommunication systems, such as equipment and systems connected to public telephone networks. The term ''phreak'' is a ...
William Quinn, also known as "decoder", was arrested and charged with accessing
Verizon
Verizon Communications Inc., commonly known as Verizon, is an American multinational telecommunications conglomerate and a corporate component of the Dow Jones Industrial Average. The company is headquartered at 1095 Avenue of the Americas in ...
's DATU numbers on over 100 occasions. Verizon subsequently claimed in press releases that it spent $120,000 to change the passwords on all the DATU numbers (it is unclear if this represented Verizon changing the DATU passwords from the default and if so why this had not been done at time of initial installation).
[http://www.computerworld.com/securitytopics/security/cybercrime/story/0,10801,94512,00.html Computer World, July 13, 2004]
References
Phreaking
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