Direct Communications Link (DCL)
The Washington-Moscow Hotline is a Direct Communication Link (DCL)
between the US and the Soviet Union, that allows the two countries to
contact each other quickly in case of a crisis (e.g. during the Cold War).
The line was established in 1963, a year after the
Cuban Missile Crisis
that nearly led to the outbreak of a nuclear war.
The hotline initially consisted of a
double teleprinter link (telex),
but was later replaced by facsimile units and eventually by
Contrary to popular believe, the Hotline was never
a red phone
that could simply be picked up to speak with the leader at the other end.
Although speech conversations are possible nowadays, probably using the
Direct Voice Link (DVL),
these links are not part of the Hotline (DCL).
We are indebted to Peter Koop , who's
and help have inspired us to compile this page.
The idea for a hotline between the USA and the USSR dates back to 1954,
when both powers realized that a direct communication line was needed
in order to prevent a nuclear war. Both countries had created enormous
stockpiles of nuclear weapons immediately after WWII had ended
and the Cold War had begun. Both countries were also in a constant
state of readiness .
Thousands of long-range ballistic missiles with nuclear
charges were buried deep underground in silos and were
carried aboard submarines. At any given moment, the world
was no more than 30 minutes away from an all-out nuclear war.
Although several parties and individuals had warned the two
countries, and both of them
took part in the Conference of Experts on Surprise Attacks in Geneva
(Switzerland) in 1958, not much happened in the following years.
The cog wheels moved very slowly during the Cold War, and military advisors
at both sides didn't want their leaders to communicate directly.
All that changed during the Cuban Missile Crisis of October 1962.
For two weeks the world balanced on the edge of war, whilst US President
John F. Kennedy had to decide whether to attack, or negotiate through
alternative diplomatic channels.
Kennedy decided to take the diplomatic route, but faced serious
communication problems when negotiating with the USSR. It took the US,
for example, nearly 12 hours to receive and decode the initial
settlement message that contained approx. 3,000 words.
By the time the message was decoded
and an answer had been prepared, another - more agressive - message had
Kennedy rescued the situation by ignoring the second letter,
pretending he never received it, and answering the first one instead.
It worked, and the Cuban Missile Crisis came to an end.
Once the dust of the event had settled, it was decided that a more
direct line of communication between the US and the USSR had to be
established. It would allow the leaders of the two countries to contact
each other in the event of a serious threat, a malfunction or an accident.
Both countries recognized the necessity of creating a direct line,
and after some negotiations, an agreement was signed
in Geneva (Switzerland) on 20 June 1963. The link became operational
less then a month later, on 13 July 1963, and was officially called
Direct Communications Link (DCL).
The communication link was also known by US technicians as the
MOLINK (Moscow Link).
The first implementation of the hotline consisted of two full-duplex
teleprinter links, one of which was a backup. Each side got
two teleprinters with the Latin alphabet and two with the Cyrillic
(Russian) alphabet. At each side, the lines were protected by four
ETCRRM cipher machines.
Rather than using American or Russian cipher machines for the encryption
of the messages, the ETCRRM machines
were built in Norway by STK
1, who was
considered neutral and impartial. STK delivered the machines with
sufficient supplies for one year and full documentation.
The image above shows the Hotline terminal room of the
NMCC at the Pentagon
on 9 July 1976. Two pairs of (black) ETCRRM machines, in a mirrored arangement,
are clearly visible.
Each pair is accompanied by a Teletype machine
for messages in the American language and an East-German T-63 2
in a wooden cabinet (at the foreground) for messages in Russian (Cryllic,
see note 2) .
Barely visible at the extreme left, are two
Siemens M-190 cipher machines
that had already been installed and were under test at that time.
A few years later they would replace the ETCRRMs.
As the ETCRRM is a One-Time Tape machine (OTT),
it uses the principle of the One-Time Pad (OTP).
When used in combination with truely random
key tapes, an OTT machine is absolutely safe and unbreakable.
As the Russians insisted on producing their own keys,
it was decided that each side would create their own key tapes.
These key tapes were then delivered by special couriers
to the embassy at the other end, who then delivered it at the other party's
So, the American Embassy in Moscow delivered their key tapes at
the Moscow hotline terminal.
Both Latin and Cyrillic teleprinters were installed at either end,
allowing each party to write in their own language.
This was considered good practice, as it would avoid miscommunications
and allowed some extra time for correct interpretation of the messages.
The first message that was sent by the Americans on the opening
day, was the well-known test message
THE QUICK BROWN FOX JUMPED OVER THE LAZY DOG'S BACK 1234567890,
a line that contains all letters of the alphabet.
The Soviets replied by sending a poetic description
of the setting Moscow sun.
The image above shows the layout of the keyboard of the Russian teleprinter,
which was in fact an East-German T-63 , that was delivered to the
Pentagon in Washington on 26 August 1963. The image was released
as a press photo by AP Wirephoto , with the following text:
WASHINGTON, Aug. 26 --ONLY THE NUMBERS ARE THE SAME-- This is the
keyboard of a Soviet teleprinter delivered to the Pentagon in
Washington today for use on the Washington-Moscow "hot line" of
communications. Russian alphabet characters are on the bottom three
lines of keys. Numbers at the top are the same as in English.
Messages will be sent and received in both Russian and English as a
protection against translations errors.
The physical link between the two terminals, ran from Washington to
London, using the first Transatlantic Cable No. 1 (TAT-1) ,
and from there via Copenhagen, Stockholm and Helsinki to Moscow.
Although the link was cryptographically safe, it was accidently cut
several times, for example when a Finnish farmer accidently ploughed
it up with a bulldozer .
In London, the line was routed through a secure telephone exchange
in the Kingsway Tunnels, a large underground complex.
The complete route is shown in the image above.
Apart from the cable link described above, there was a full-duplex
radio link that was used as a backup. It ran from Washington via
Tangier (Morocco) to Moscow and vice versa. This alternative route
is dotted in the above drawing. It was also used for service
communications. Both links were tested daily.
At the time, STK was an independent subsidary of the American ITT
It is sometimes erroneously thought that the Cyrillic T-63/SU teleprinter
was made by Siemens in East Germany. This was not the case however,
as there was no Siemens factory behind the Iron Curtain at the time.
The T-63 was built by
VEB RFT Messgerätewerk Zwönitz,
but was based on the earlier RFT T-51,
which in turn was an East-German copy of the Siemens T-37.
It is also known as T63/SU12 and as T63/RU,
and was able to switch between Latin and Cyrillic characters .
On 30 September 1971, the US and the USSR agreed to improve the
reliability of the DCL (Hotline) by giving up the radio link and
installing two additional circuits: one installed by the US via the
commercial geosynchronous Intelsat IV Satellite System,
and other one installed by the USSR
using four of their Molniya II Satellites in a high elliptical orbit.
Installation and testing of the new links took several years, but finally
they became operational on 16 January 1978.
The new satellite links appeared to be
far less vulnerable than the original cables through Europe.
At the same time the number of terminals was increased on each side,
to a series of terminals at unspecified locations. In the US, there
were the usual terminals at the NMCC,
and at the White House
The locations of the Soviet terminals are currently unknown.
It was agreed that any messages received via the DCL would be
communicated to the 'head of government'.
1980: New teleprinter equipment
In 1980, the DCL received a facelift when the Teletype terminals
were replaced by newer models and the valve-based
ETCRRM cipher machines were replaced
by compatible solid-state Siemens M-190
units. Although the M-190 was rather old
(it was developed in the early 1960s), it
was relatively modern in comparison to the ETCRRM that was developed
some ten years earlier.
The M-190 units had been installed at the opposite wall of the room
as early as 1976, and had been tested for several years before
they were approved for duty and moved to the current position.
The image above shows the DCL room in the NMCC at the Pentagon.
The Siemens M-190 is clearly visible
in the foreground, whilst an operator is typing a message on one
of the Teletype machines.
The picture was taken on 2 August 1985, shortly before the next
upgrade of the DCL.
1985: Facsimile equipment
On 17 July 1984, the US and the USSR signed an agreement to
upgrade the DCL with facsimile equipment, following negotiations
that had started in May 1983 on the initiative of President Reagan.
It was agreed that identical Group III faxes, running at
4800 baud, were installed at both ends.
In addition to printed text, the fax was capable of sending handwritten
messages, charts, maps and photographs, and could transfer a page in
6 to 15 seconds, typically 12 times faster than a teleprinter.
Mid-1985 the links became operational and were tested for several years.
At the same time, the USSR upgraded their part of the link to
a newer geosynchronous Gorizont-class satellite, as a result of which
the Americans no longer had to switch between Molniya satellites every
four hours. In 1996, the Russians would upgrade to a new Molniya III satellite.
The image above shows the opposite wall of the DCL terminal room
in the NMCC at the Pentagon on 14 November 1985, a few months after
the facsimile equipment had become operational. Below each scanner,
an IBM PC is installed for the One-Time Pad (OTP)
encryption of the data. For this purpose, the US also supplied
the IBM PCs and the fax machines to the USSR.
In the foreground, the Siemens M-190
cipher machine is still visible,
which proves that the picture was taken in the same room as the previous one.
For several years the M-190 teleprinter line remained the primary link
between the US and the USSR, until the fax link was found reliable enough
to replace it. Finally, in 1988, the teleprinter link was shut down .
In 2007, work started on another upgrade of the Direct Communication Link
(DCL). The earlier data link was replaced by a dedicated computer network
with e-mail and chat functionality. While the chat function is used by
the operators for the coordination of the link, e-mails are used for the
official part. The e-mail system allows text messages, scanned images
and files to be sent.
At the same time, the old cable link was replaced by a new optic-fiber
link, allowing the two satellite links to be used as redundant circuits.
Back in 1996, the Russians had already upgraded their part of the satellite
link by replacing the Gorizont satellite channel by a Molnyia III one.
The upgrade became operational in 2008 and allows messages and data to be
sent near to real-time.
The image above was taken at the event of the 50th anniversary of
the Hotline on 30 August 2013, and shows what it looks like today.
The old teleprinters and IBM PCs have made room for modern computers
with secure e-mail. The man standing towards the rear is Lt. Col.
Charles Cox, the senior presidential translator. Sitting in front of
him is Navy Chief Petty Officer John E. Kelley, a presidential communicator.
For safety reasons, there were three Hotline terminals on the
The primary terminal is at the National Military Command Center (NMCC)
in the Pentagon. It is manned 24/7 in four 8-hour shifts by NMCC personnel
and is under control of the Joint Chiefs of Staff. The NMCC is responsible
for the daily testing of the link and for the translation of any messages
that are transmitted or received.
- White House
Initially, there was no terminal at the White House, but when the
Russians sent their first message in 1967 (at the event of the Six Day
War between Egypt and Israel), Defense Secretary Robert McNamara
ordered a quick patch from the Pentagon to the White House.
This temporary link was later replaced by an ancillary terminal that was installed
in the Military Communications Center of the White House Communications Agency
(WHCA). The White House terminal has an override facility that allow it
to lock-out other terminals.
- Raven Rock Mountain
A third terminal was located at the Alternate National Military Command
Center (ANMCC), the Pentagon's backup site, located in the Raven Rock
Mountain. It is operated by NMCC personnel and is tested periodically.
According to a SECRET directive of September 1985, signed by
President Ronald Reagan, the President could at any time appoint new
locations for additional Hotline terminals, the location of which would
be classified as SECRET. Whether or not this has happened is currently
At present it is unclear what the exact location of the terminal in
Moscow was. Although it was meant to be in the Kremlin, close to the
office of the Prime Minister, there are indications that it was instead
opposite the Read Square at the Communist Party Headquarters .
Unlike in America, the Russian terminal was operated by civilians.
Contrary to popular believe, the hotline was never a red phone that was
used for voice (speech) communication between Washington and Moscow in the
event of an emergency. Nevertheless, a typical red phone is on public display
at the Jimmy Carter Library and Museum in Atlanta (USA).
The image on the right shows that particular red phone.
The phone has no dial (which is common for hotline phones) and is mounted
on a pole with a placard at the bottom, claiming that it was used on the
Moscow-Washington hotline during the Carter Administration in the White House.
Unfortunately, the sign is wrong as this was never the case.
Although it is entirely possible that the phone was used for
another kind of hotline communication during the time of the
Carter Administration, for example for a direct link with the Pentagon,
it was definitely not used on the DCL; the Washington-Moscow Hotline.
Nevertheless, the idea of a red phone being used for hotline communication
persisted, not least because of the many blockbuster movies in which the
world leaders contact each other in crisis situations. For this reason, the
Washington-Moscow Hotline is often referred to as the Red Phone.
There are several reasons for not having direct voice communications at
times of crisis. First of all, it was very difficult, if not impossible,
during the 1960s to have reliable
secure voice encryption
on such lines, without
revealing (secret) technology. The most important reason however, is to
avoid misunderstandings caused by the language barrier. Sending written
messages (by teleprinter, fax or computer) allows time for proper translation
Since the 1990s, it is possible to have a direct voice conversation with
the other end, but this is not considered part of the Hotline.
It is likely that for voice coversations the so-called Direct Voice Link
(DVL) is used. This link has terminals at both ends near the offices of the
Presidents and is routed (multiplexed) over the same satellite links
as the DCL.
The DVL is normally used for diplomatic and scheduled traffic, but can be
used in crisis situations by special arrangement.
The Hotline was mainly intended to inform the other party in case of
incidents, (nuclear) accidents and unexpected moves of fleet and troups,
which the other party could see as a provocation or as an act of war.
Only a few months after the DCL became operational, it was first used
by the Americans on 22 November 1963, when President John F. Kennedy was
The Hotline was used during the following international conflicts:
- 1963 Assassination of President Kennedy
- 1967 Six Day War between Egypt and Israel
- 1971 War between India and Pakistan
- 1973 Yom Kippur War
- 1974 Turkish Invasion of Cyprus
- 1979 Russian Invasian of Afganistan
- 1981 Threat of Russian Invasion of Poland
- 1982 Israeli Invasion of Lebanon
- 1991 Gulf War
- 2003 Aftermath of Iraq War
The first official use of the Hotline by the Russians was on 5 June 1967,
at the outbreak of the Six Day War between Egypt and Israel. It was the
first of a total of 20 messages that were exchanged during this event.
Three of these messages were related to the so-called Liberty Incident ;
the apparantly accidental attack of the USS Liberty by the Israeli Defence Forces
on 8 June 1967.
The leftmost image above shows the
that was sent by the USSR
via the Hotline, informing the US that they were seeking to end the conflict
as soon as possible, and asking the US to do the same. The letter is written
in Russian and is signed by Minister A. Kosygin.
At the right is the
of the letter, created by the White House interpretors .
National Military Command Center
Responsible for operation, maintenance and testing of the Hotline (DCL).
Also the primary terminal of the US side of the Hotline.
Located at the Pentagon in Washington.
Alternate National Military Command Center
Backup command center of the Pentagon, also the backup terminal of the
Hotline (DCL), located in Raven Rock Mountain.
White House Communications Agency
Official communications agency of the White House. Also responsible
for operating the secundary terminal of the US side of the Hotline (DCL).
Direct Communications Link
Official name of the Washington-Moscow Hotline.
Direct Voice Link
Voice communication link, running on the same network, but not part of,
- Peter Koop, The Washington-Moscow Hot Line
Retrieved January 2013.
- Matt Dattilo, Washington-Moscow Hotline Established, June 20, 1963
21 June 2011. Retrieved January 2013.
- AP, Photograph of Siemens M-190 and teletypes in the Hotline room
27 August 1985. Retrieved November 2012. Image kindly supplied by .
- Scott Davis, Images of Us-Soviet Hotline
© Time Inc. LIFE magazine, 14 November 1985, Arlington, VA, USA.
Retrieved January 2013.
- Wikipedia, TAT-1, Transatlantic Cable Number 1
Retrieved Januari 2013.
- Ronald Reagan, National Decision Directive Number 186
4 September 1985. SECRET. Declassified 10 June 2011.
- US Department of State, Agreement Between the USA and the USSR to upgrade the DCL
17 July 1984. Retrieved January 2013.
- Dan Merica, If these Walls Could Talk: Installing a direct line to Moscow
CNN Politics website, 27 August 2012.
- Hugo Ryvik, Thales, On a Secret Mission. 50 years of Norwegian cryptology.
Thales, private publication, 2005.
- A. Jay Cristol, The Liberty Incident
July 2007. Retrieved Januari 2013.
- NARA, Letter from A. Kosygin to the US President via Soviet Molink
5 June 1963. Confidential. Declassified 7 February 1996.
- Joachim Beckh, Blitz & Anker, Band 1: Informationstechnik - Geschichte und Hintergründe
Backgrounds on the T-63 teleprinter (German). [Thanks to Jim Meyer
for pointing this out]
ISBN 3-8334-2996-8. p. 119.
- AP Wirephoto, Image of Russian keyboard
26 August 1963. AP Wirephoto #b21455kwg. Crypto Museum archive #CM301762.
- US Army, Hotline, now 50 years old...
Website. Retrieved September 2013.
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© Crypto Museum. Created: Sunday 27 January 2013. Last changed: Sunday, 29 November 2015 - 10:53 CET.