HOME

TheInfoList



OR:

The ''tap code'', sometimes called the knock code, is a way to encode text messages on a letter-by-letter basis in a very simple way. The message is transmitted using a series of tap sounds, hence its name. The tap code has been commonly used by prisoners to communicate with each other. The method of communicating is usually by tapping either the metal bars, pipes or the walls inside a cell.


Design

The tap code is based on a Polybius square using a 5×5 grid of letters representing all the letters of the
Latin alphabet The Latin alphabet, also known as the Roman alphabet, is the collection of letters originally used by the Ancient Rome, ancient Romans to write the Latin language. Largely unaltered except several letters splitting—i.e. from , and from � ...
, except for K, which is represented by C. Each letter is communicated by tapping two numbers, the first designating the row and the second (after a pause) designating the column. For example, to specify the letter "B", one taps once, pauses, and then taps twice. The listener only needs to discriminate the timing of the taps to isolate letters. To communicate the word "hello", the cipher would be the following (with the pause between each number in a pair being shorter than the pause between letters): The letter "X" is used to break up sentences, and "K" for acknowledgements. Because of the difficulty and length of time required for specifying a single letter, prisoners often devise abbreviations and acronyms for common items or phrases, such as "GN" for ''Good night'', or "GBU" for ''God bless you''. By comparison, despite its messages being shorter,
Morse code Morse code is a telecommunications method which Character encoding, encodes Written language, text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code i ...
is harder to send by tapping or banging. Its short and long signals can be improvised as taps and thumps, or short and long whistles or scraping sounds, but tap codes are simpler to learn and can be used in a wider variety of situations. The tap system simply requires one to know the alphabet and the short sequence "AFLQV" (the initial letter of each row), without memorising the entire grid. For example, if a person hears four knocks, they can think "A... F... L... Q". If after a pause there are three knocks, they think "Q... R... S" to arrive at the letter S.


History

The origins of this encoding go back to the Polybius square of
Ancient Greece Ancient Greece () was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity (), that comprised a loose collection of culturally and linguistically r ...
. Like the "knock code", a
Cyrillic script The Cyrillic script ( ) is a writing system used for various languages across Eurasia. It is the designated national script in various Slavic languages, Slavic, Turkic languages, Turkic, Mongolic languages, Mongolic, Uralic languages, Uralic, C ...
version is said to have been used by nihilist prisoners of the Russian czars. The knock code is featured in
Arthur Koestler Arthur Koestler (, ; ; ; 5 September 1905 – 1 March 1983) was an Austria-Hungary, Austro-Hungarian-born author and journalist. Koestler was born in Budapest, and was educated in Austria, apart from his early school years. In 1931, Koestler j ...
's 1941 work ''
Darkness at Noon ''Darkness at Noon'' (, ) is a novel by Austrian-Hungarian-born novelist Arthur Koestler, first published in 1940. His best known work, it is the tale of Rubashov, an Old Bolshevik who is arrested, imprisoned, and tried for treason against the ...
''.
Kurt Vonnegut Kurt Vonnegut ( ; November 11, 1922 – April 11, 2007) was an American author known for his Satire, satirical and darkly humorous novels. His published work includes fourteen novels, three short-story collections, five plays, and five nonfict ...
's 1952 novel ''
Player Piano A player piano is a self-playing piano with a pneumatic or electromechanical mechanism that operates the piano action using perforated paper or metallic rolls. Modern versions use MIDI. The player piano gained popularity as mass-produced home ...
'' also includes a conversation between prisoners using a form of tap code. The code used in the novel is more primitive and does not make use of the Polybius square (e.g. "P" consists of sixteen taps in a row). United States prisoners of war during the
Vietnam War The Vietnam War (1 November 1955 – 30 April 1975) was an armed conflict in Vietnam, Laos, and Cambodia fought between North Vietnam (Democratic Republic of Vietnam) and South Vietnam (Republic of Vietnam) and their allies. North Vietnam w ...
are most known for having used the tap code. It was introduced in June 1965 by four
POWs A prisoner of war (POW) is a person held captive by a belligerent power during or immediately after an armed conflict. The earliest recorded usage of the phrase "prisoner of war" dates back to 1610. Belligerents hold prisoners of war for a ...
held in the Hỏa Lò ("Hanoi Hilton") prison: Captain Carlyle "Smitty" Harris, Lieutenant Phillip Butler, Lieutenant Robert Peel, and Lieutenant Commander Robert Shumaker. Harris had heard of the tap code being used by prisoners in World War II and remembered a
United States Air Force The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...
instructor who had discussed it as well. In Vietnam, the tap code became more widely used than Morse; despite messages taking longer to send, the system was easier to learn and could be applied in a wider variety of situations. Tap codes proved to be a very successful way for otherwise isolated prisoners to communicate. POWs would use the tap code in order to communicate to each other between cells in a way which the guards would be unable to pick up on. They used it to communicate everything from what questions interrogators were asking (in order for everyone to stay consistent with a deceptive story), to who was hurt and needed others to donate meager food rations. It was easy to teach and newly arrived prisoners became fluent in it within a few days. It was even used when prisoners were sitting next to each other but not allowed to talk, by tapping on another's thigh. U.S. Navy Rear Admiral Jeremiah Denton developed a vocal tap code of coughs, sniffs and sneezes. By overcoming isolation with the tap code, prisoners were said to be able to maintain a chain of command and keep up morale. In 1980, a doctor sentenced to life in solitary confinement in
Somalia Somalia, officially the Federal Republic of Somalia, is the easternmost country in continental Africa. The country is located in the Horn of Africa and is bordered by Ethiopia to the west, Djibouti to the northwest, Kenya to the southwest, th ...
used tap code to share the entirety of Tolstoy's '' Anna Karenina'', nearly 2 million letters, via tap code with fellow prisoners.


In popular culture

In the video game '' Metal Gear 2: Solid Snake'', the tap code is used by Dr. Drago Pettrovich Madnar to communicate to ''
Solid Snake , real name David, is a fictional character and one of the protagonists of Konami's ''Metal Gear'' series, created by Hideo Kojima. He is depicted as a former United States Army Special Forces, Green Beret and highly skilled special operations so ...
'' through a cell wall. In Season 2 Episode 2 of '' Person of Interest'', the tap code is used by Harold Finch to discreetly leave breadcrumbs of his location to John Reese by encoding his location as tap code on a telephone. In the video game '' Her Story'', the main characters use the tap code to surreptitiously communicate. In Season 2 Episode 14 of ''
The Flash The Flash is the name of several superheroes appearing in American comic books published by DC Comics. Created by writer Gardner Fox and artist Harry Lampert, the original Flash first appeared in ''Flash Comics'' #1 (cover date, cover-dated Jan ...
'', the masked prisoner in Zoom's lair uses the tap code to try to communicate with the others. In the film '' The Ice Road'', the tap code is used on a metal pipe conduit by trapped miners to communicate with executives of the mining company. In the television show ''
Breaking Bad ''Breaking Bad'' is an American crime drama television series created and produced by Vince Gilligan for AMC (TV channel), AMC. Set and filmed in Albuquerque, New Mexico, the series follows Walter White (Breaking Bad), Walter White (Bryan Cran ...
'', the character Hector Salamanca uses the version of a tap code shown in this section to communicate after suffering a
stroke Stroke is a medical condition in which poor cerebral circulation, blood flow to a part of the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemor ...
. In an ARG for Cool Math Games, (See Game Theory for more information), a tap code was used twice, once in pair with another cypher to solve and discover lore.


See also

*
Morse code Morse code is a telecommunications method which Character encoding, encodes Written language, text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code i ...


References


External links


Online Tap Code Encoder/Decoder

L' Alfabeto Quadrato(Codice a Colpi) - An Degrida
Artist An Degrida's Tap Code artistic illustration. {{Cryptography navbox , classical Classical ciphers Encodings