Autovon
Encyclopedia
AUTOVON, short for Automatic Voice Network, was an American
military phone system built in 1963 to survive nuclear attacks. AUTOVON was first established in the United States, using the Army's SCAN (Switch Communications Automated Network) system. Around the mid-1970s AUTOVON expanded to the United Kingdom
, Asia
, the Middle East
, and Panama
. It was a major part of the Defense Communications System (DCS), providing non-secure switched voice services. Today the system is unused, replaced in the early 1990s by the Defense Switched Network
.
coaxial multiplex built by AT&T
, who also used them to carry about one third of all civilian long-distance lines as well, as they were much bigger than the military needed. Although unused, some of the cables remain today and the routes are easily visible on satellite photos. The system was transported over many media other than underground cable, including microwave
, open wire and, near the end of the system's life, fiber optic. Exaggerated stories of underground concrete cable ducts are in circulation but most of the cable was directly buried without any added concrete, relying instead on the natural protection of dirt.
Most of the cable repeater huts have been sold to private interests, to round out existing parcels, or as possible build-to-suit tower sites, etc. AT&T
is now filling the small underground portion before sale, unless they sell to a major company. The junctions for AUTOVON are also being sold into private ownership, with a few exceptions. Most are stripped of all the equipment, although the AUTOVON junction in Mounds, Oklahoma
was sold with all the old equipment still in place.
Switches
were initially a 4 wire version of 5XB switch, replaced in the early 1970s after the more versatile 1ESS switch
had shown its reliability.
, with the system typically sending the reorder tone
("fast-busy" signal) to indicate the problem. Such an event was not acceptable for a military network where some messages absolutely have to get through.
To address this problem, AUTOVON included four precedence levels: Routine, Priority, Immediate and Flash, plus an additional capability: Flash Override. A normal call was equivalent to Routine, and calls of increasing precedence could knock down calls of lower priority (giving them a special tone) if need be, which was called preemption. For instance, if the call was placed with Flash precedence and was switched to a route where all trunks were in use, the switch would then preempt a Routine call if there was one, and then Priority and Immediate. Only in the case where a switch's lines were all being used by Flash or Flash Override would the user receive a reorder signal.
When a user wanted to place a call normally, they would simply dial the number. However, if the call was to be placed with precedence, a key in the rarely used and rarely seen 1633 Hz column of DTMF
tones would be pressed before dialing to assign this:
There were complex regulations as to who was allowed these precedence levels. Flash Override was not officially a precedence level, but rather a capability designed to allow the President of the United States
or other National Command Authority
to preempt any other traffic in the network in an emergency. See also Multilevel precedence and preemption
. The network had its own three-digit "area codes" for various geographic regions around the world. The area codes each included several three digit exchange codes, usually corresponding to the central office telephone switches serving each installation. Thus, almost any telephone on a military base could be direct-dialed via AUTOVON. A selected set of telephones were four wire
AUTOVON phones, wired directly into the AUTOVON network. Others could initiate AUTOVON calls with operator assistance.
Though the numbering plan
was similar to the U.S. civilian scheme, the routing structure was a very complex polygrid system unlike the civilian office classification scheme. It was barely within the information processing capabilities of the 5XB switch which implemented it. The non-hierarchical routing structure was intended to get around any number of nodes destroyed in war. This system inspired similarly survivable ones for message networks, including in future decades the Internet
.
Local base switches would be connected to a few AUTOVON trunks, which the user would access by dialing 8 (or in some cases, 88) as the first digit. To dial locally a user would dial 9, and to dial using commercial long-distance, 1 (where this was supported). The United States Department of Defense
(DoD) drew up a complex billing system in order to charge for access to AUTOVON, and each base budgeted as they saw fit.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
military phone system built in 1963 to survive nuclear attacks. AUTOVON was first established in the United States, using the Army's SCAN (Switch Communications Automated Network) system. Around the mid-1970s AUTOVON expanded to the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...
, and Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...
. It was a major part of the Defense Communications System (DCS), providing non-secure switched voice services. Today the system is unused, replaced in the early 1990s by the Defense Switched Network
Defense Switched Network
The Defense Switched Network is a primary information transfer network for the Defense Information Systems Network . The DSN provides the worldwide non-secure voice, secure voice, data, facsimile, and video teleconferencing services for DOD Command and Control elements, their supporting...
.
Lines
AUTOVON used a combination of its own constructed lines and other lines operated by AT&T and smaller independent telephone companies, connected to exchanges located far from other civilian or military targets. In the US the cables were predominantly L-carrierL-carrier
SystemYearFrequencyCoax per cableDistance between repeatersVoice circuits per coax tubeL-119413 MHz48 miles600L-21942840 kHz416 miles360L-319508 MHz84 miles1,860L-4196717 MHz202 miles3,600L-5197257 MHz221 mile10,800L-5E197566 MHz221 mile13,200...
coaxial multiplex built by AT&T
AT&T
AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...
, who also used them to carry about one third of all civilian long-distance lines as well, as they were much bigger than the military needed. Although unused, some of the cables remain today and the routes are easily visible on satellite photos. The system was transported over many media other than underground cable, including microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
, open wire and, near the end of the system's life, fiber optic. Exaggerated stories of underground concrete cable ducts are in circulation but most of the cable was directly buried without any added concrete, relying instead on the natural protection of dirt.
Most of the cable repeater huts have been sold to private interests, to round out existing parcels, or as possible build-to-suit tower sites, etc. AT&T
AT&T
AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...
is now filling the small underground portion before sale, unless they sell to a major company. The junctions for AUTOVON are also being sold into private ownership, with a few exceptions. Most are stripped of all the equipment, although the AUTOVON junction in Mounds, Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...
was sold with all the old equipment still in place.
Switches
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...
were initially a 4 wire version of 5XB switch, replaced in the early 1970s after the more versatile 1ESS switch
1ESS switch
The Number One Electronic Switching System, the first large-scale Stored Program Control telephone exchange or Electronic Switching System in the Bell System, was introduced in Succasunna, New Jersey, in May 1965. The switching fabric was composed of reed matrixes controlled by wire spring relays...
had shown its reliability.
Precedence
One interesting feature of the AUTOVON system was the inclusion of precedence for calls. In the civilian networks if there are no free lines the caller is unable to reach the called partyCalled party
The called party is a person who answers a telephone call. The person who initiates a telephone call is the calling party....
, with the system typically sending the reorder tone
Reorder tone
The reorder tone, also known as the fast busy tone, is the congestion tone or all trunks busy tone of a public switched telephone network. It varies from country to country; in the USA it is a dual-frequency tone of 480 Hz and 620 Hz at a cadence of 0.25 seconds on, 0.25 off; that is two beeps per...
("fast-busy" signal) to indicate the problem. Such an event was not acceptable for a military network where some messages absolutely have to get through.
To address this problem, AUTOVON included four precedence levels: Routine, Priority, Immediate and Flash, plus an additional capability: Flash Override. A normal call was equivalent to Routine, and calls of increasing precedence could knock down calls of lower priority (giving them a special tone) if need be, which was called preemption. For instance, if the call was placed with Flash precedence and was switched to a route where all trunks were in use, the switch would then preempt a Routine call if there was one, and then Priority and Immediate. Only in the case where a switch's lines were all being used by Flash or Flash Override would the user receive a reorder signal.
When a user wanted to place a call normally, they would simply dial the number. However, if the call was to be placed with precedence, a key in the rarely used and rarely seen 1633 Hz column of DTMF
Dual-tone multi-frequency
Dual-tone multi-frequency signaling is used for telecommunication signaling over analog telephone lines in the voice-frequency band between telephone handsets and other communications devices and the switching center. The version of DTMF that is used in push-button telephones for tone dialing is...
tones would be pressed before dialing to assign this:
- A (697/1633, FO): Flash Override
- B (770/1633, F): Flash
- C (852/1633, I): Immediate
- D (941/1633, P): Priority
There were complex regulations as to who was allowed these precedence levels. Flash Override was not officially a precedence level, but rather a capability designed to allow the President of the United States
President of the United States
The President of the United States of America is the head of state and head of government of the United States. The president leads the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces....
or other National Command Authority
National Command Authority
National Command Authority is a term used by the Department of Defense of the United States of America to refer to the ultimate lawful source of military orders. The NCA comprises the President of the United States and the Secretary of Defense jointly, or their duly deputized successors, i.e...
to preempt any other traffic in the network in an emergency. See also Multilevel precedence and preemption
Multilevel precedence and preemption
In military communications, Multilevel Precedence and Preemption is a priority scheme for assigning one of several precedence levels to specific calls or messages so that the system handles them in a predetermined order and time frame, for gaining controlled access to network resources in which...
Numbering plan
AUTOVON used a 3-3-4 numbering scheme similar to the North American Numbering PlanNorth American Numbering Plan
The North American Numbering Plan is an integrated telephone numbering plan administered by Neustar which encompasses 24 countries and territories, including the United States and its territories, Canada, Bermuda, and 16 nations of the Caribbean...
. The network had its own three-digit "area codes" for various geographic regions around the world. The area codes each included several three digit exchange codes, usually corresponding to the central office telephone switches serving each installation. Thus, almost any telephone on a military base could be direct-dialed via AUTOVON. A selected set of telephones were four wire
Four-wire circuit
In telecommunication, a four-wire circuit is a two-way circuit using two paths so arranged that the respective signals are transmitted in one direction only by one path and in the other direction by the other path...
AUTOVON phones, wired directly into the AUTOVON network. Others could initiate AUTOVON calls with operator assistance.
Though the numbering plan
Telephone numbering plan
A telephone numbering plan is a type of numbering scheme used in telecommunications to allocate telephone numbers to subscribers and to route telephone calls in a telephone network. A closed numbering plan, such as found in North America, imposes a fixed total length to numbers...
was similar to the U.S. civilian scheme, the routing structure was a very complex polygrid system unlike the civilian office classification scheme. It was barely within the information processing capabilities of the 5XB switch which implemented it. The non-hierarchical routing structure was intended to get around any number of nodes destroyed in war. This system inspired similarly survivable ones for message networks, including in future decades the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
.
Local base switches would be connected to a few AUTOVON trunks, which the user would access by dialing 8 (or in some cases, 88) as the first digit. To dial locally a user would dial 9, and to dial using commercial long-distance, 1 (where this was supported). The United States Department of Defense
United States Department of Defense
The United States Department of Defense is the U.S...
(DoD) drew up a complex billing system in order to charge for access to AUTOVON, and each base budgeted as they saw fit.
See also
- Autodin Contemporaneous military data network
- AutosevocomAutomatic Secure Voice Communications NetworkAutomatic Secure Voice Communications Network : A worldwide, switched, secure voice network developed to fulfill DoD long-haul, secure voice requirements. See AUTOVON for a similar, but non-secure voice system....
(Automatic Secure Voice Communications Network), similar to Autovon, but secure.
