The Baudot code[boˈdo] is an early character encoding for telegraphy invented by Émile Baudot in the 1870s. It was the predecessor to the International Telegraph Alphabet No. 2 (ITA2), the most common teleprinter code in use until the advent of ASCII. Each character in the alphabet is represented by a series of five bits, sent over a communication channel such as a telegraph wire or a radio signal. The symbol rate measurement is known as baud, and is derived from the same name.
Radioteletype (RTTY) is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations connected by radio rather than a wired link. Radioteletype evolved from earlier landline teleprinter operations that began in the mid-1800s. The US Navy Department successfully tested printing telegraphy between an airplane and ground radio station in 1922. Later that year, the Radio Corporation of America successfully tested printing telegraphy via their Chatham, Massachusetts, radio station to the R.M.S. Majestic. Commercial RTTY systems were in active service between San Francisco and Honolulu as early as April 1932 and between San Francisco and New York City by 1934. The US military used radioteletype in the 1930s and expanded this usage during World War II. From the 1980s, teleprinters were replaced by personal computers (PCs) running software to emulate teleprinters.
A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user. The term is derived from Greek: τῆλε and φωνή, together meaning distant voice. A common short form of the term is phone, which came into use almost immediately after the first patent was issued.
A teleprinter is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initially they were used in telegraphy, which developed in the late 1830s and 1840s as the first use of electrical engineering, though teleprinters were not used for telegraphy until 1887 at the earliest. The machines were adapted to provide a user interface to early mainframe computers and minicomputers, sending typed data to the computer and printing the response. Some models could also be used to create punched tape for data storage and to read back such tape for local printing or transmission.
A universal asynchronous receiver-transmitter is a computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable. It sends data bits one by one, from the least significant to the most significant, framed by start and stop bits so that precise timing is handled by the communication channel. The electric signaling levels are handled by a driver circuit external to the UART. Two common signal levels are RS-232, a 12-volt system, and RS-485, a 5-volt system. Early teletypewriters used current loops.
In computing, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel. Throughout most of the history of personal computers, data has been transferred through serial ports to devices such as modems, terminals, various peripherals, and directly between computers.
Asynchronous serial communication is a form of serial communication in which the communicating endpoints' interfaces are not continuously synchronized by a common clock signal. Instead of a common synchronization signal, the data stream contains synchronization information in form of start and stop signals, before and after each unit of transmission, respectively. The start signal prepares the receiver for arrival of data and the stop signal resets its state to enable triggering of a new sequence.
A busy signal in telephony is an audible call-progress tone or audible signal to the calling party that indicates failure to complete the requested connection of that particular telephone call.
The Hellschreiber, Feldhellschreiber or Typenbildfeldfernschreiber is a facsimile-based teleprinter invented by Rudolf Hell. Compared to contemporary teleprinters that were based on typewriter systems and were mechanically complex and expensive, the Hellschreiber was much simpler and more robust, with far fewer moving parts. It has the added advantage of being capable of providing intelligible communication even over very poor quality radio or cable links, where voice or other teledata would be unintelligible.
Store and forward is a telecommunications technique in which information is sent to an intermediate station where it is kept and sent at a later time to the final destination or to another intermediate station. The intermediate station, or node in a networking context, verifies the integrity of the message before forwarding it. In general, this technique is used in networks with intermittent connectivity, especially in the wilderness or environments requiring high mobility. It may also be preferable in situations when there are long delays in transmission and variable and high error rates, or if a direct, end-to-end connection is not available.
The TSEC/KW-26, code named ROMULUS, was an encryption system used by the U.S. Government and, later, by NATO countries. It was developed in the 1950s by the National Security Agency (NSA) to secure fixed teleprinter circuits that operated 24 hours a day. It used vacuum tubes and magnetic core logic, replacing older systems, like SIGABA and the British 5-UCO, that used rotors and electromechanical relays.
The KW-37, code named JASON, was an encryption system developed In the 1950s by the U.S. National Security Agency to protect fleet broadcasts of the U.S. Navy. Naval doctrine calls for warships at sea to maintain radio silence to the maximum extent possible to prevent ships from being located by potential adversaries using radio direction finding. To allow ships to receive messages and orders, the navy broadcast a continuous stream of information, originally in Morse code and later using radioteletype. Messages were included in this stream as needed and could be for individual ships, battle groups or the fleet as a whole. Each ship's radio room would monitor the broadcast and decode and forward those messages directed at her to the appropriate officer. The KW-37 was designed to automate this process. It consisted of two major components, the KWR-37 receive unit and the KWT-37 transmit unit. Each ship had a complement of KWR-37 receivers that decrypted the fleet broadcast and fed the output to teleprinter machines. KWT-37's were typically located at shore facilities, where high power transmitters were located.
In concurrent programming, a monitor is a synchronization construct that allows threads to have both mutual exclusion and the ability to wait (block) for a certain condition to become false. Monitors also have a mechanism for signaling other threads that their condition has been met. A monitor consists of a mutex (lock) object and condition variables. A condition variable essentially is a container of threads that are waiting for a certain condition. Monitors provide a mechanism for threads to temporarily give up exclusive access in order to wait for some condition to be met, before regaining exclusive access and resuming their task.
In data communications, flow control is the process of managing the rate of data transmission between two nodes to prevent a fast sender from overwhelming a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed with data from transmitting node. Flow control should be distinguished from congestion control, which is used for controlling the flow of data when congestion has actually occurred. Flow control mechanisms can be classified by whether or not the receiving node sends feedback to the sending node.
A mountza or moutza also called faskeloma is the most traditional gesture of insult among Greeks. It consists of extending and spreading all fingers of the hand and presenting the palm towards the face of the person to be insulted with a forward motion.
GE Marc V is a historic U.S. format or protocol of trunked, two-way radio introduced by General Electric Mobile Radio in the early 1980s. This equipment was also sold in Australia. The product name looks and sounds similar to GE-Mark V, a turbine controller made by General Electric. GE developed the EDACS radio system based on its success with Marc V.
KPH is a public coast radio station on the West Coast of the United States. For most of the 20th century, it provided ship to shore communications including telegrams and marine telex service. The station discontinued commercial operation in 1998, but is operated occasionally as a historic service – its signal can be tuned in throughout a large portion of the western hemisphere.
The telex network is a customer-to-customer switched network of teleprinters similar to a telephone network, using telegraph-grade connecting circuits for two-way text-based messages. Telex was a major method of sending written messages electronically between businesses in the post-World War II period. Its usage went into decline as the fax machine grew in popularity in the 1980s.
C. Lorenz AG (1880-1958) was a German electrical and electronics firm primarily located in Berlin. It innovated, developed and marketed products for electric lighting, telegraphy, telephony, radar, and radio. It was acquired by ITT in 1930, and became part of the newly founded company Standard Elektrik Lorenz (SEL), Stuttgart in 1958 when it merged with Standard Elektrizitätsgesellschaft and several other smaller companies owned by ITT. In 1987, SEL merged with the French companies Compagnie Générale d'Electricité and Alcatel to form the new Alcatel SEL.
Werner Liebknecht was a German engineer and Beamter who was Director of Engineering at Referat Wa Prüf 7 of the Waffenamt during World War II and who was responsible for the design and development of many of the cryptographic devices used by German Armed Forces during World War II, including the cipher teleprinter attachment, the SZ 40 and the Siemens and Halske T52 secure teleprinter.
This article incorporates public domain material from the General Services Administration document: "Federal Standard 1037C".