A hydraulic telegraph (Greek: υδραυλικός τηλέγραφος) is either of two different hydraulic-telegraph telecommunication systems. The earliest one was developed in 4th-century BC Greece, while the other was developed in 19th-century AD Britain. The Greek system was deployed in combination with semaphoric fires, while the latter British system was operated purely by hydraulic fluid pressure.
Although both systems employed water in their sending and receiver devices, their transmission media were completely different. The ancient Greek system transmitted its semaphoric information to the receiver visually, which limited its use to line-of-sight distances in good visibility weather conditions only. The 19th-century British system used water-filled pipes to effect changes to the water level in the receiver unit (similar to a transparent water-filled flexible tube used as a level indicator), thus limiting its range to the hydraulic pressure that could be generated at the transmitter's device.
While the Greek device was extremely limited in the codes (and hence the information) it could convey, the British device was never deployed in operation other than for very short-distance demonstrations. The British device could, however, be used in any visibility within its range of operation so long as its conduits, if unheated, did not freeze in sub-zero temperatures —which contributed to its impracticality.
The ancient Greek design was described in the 4th century BC by Aeneas Tacticus and the 3rd century BC by the historian Polybius. According to Polybius, it was used during the First Punic War to send messages between Sicily and Carthage.
The system involved identical containers on separate hills, which are not connected to each other; each container would be filled with water, and a vertical rod floated within it. The rods were inscribed with various predetermined codes at various points along its height.
To send a message, the sending operator would use a torch to signal the receiving operator; once the two were synchronized, they would simultaneously open the spigots at the bottom of their containers. Water would drain out until the water level reached the desired code, at which point the sender would lower his torch, and the operators would simultaneously close their spigots. Thus the length of time the sender's torch was visible could be correlated with specific predetermined codes and messages.
He says that those who are about to [communicate] urgent news to each other by fire signal should procure two earthenware vessels of exactly the same width and depth, the depth being some three cubits and the width one. Then they should have corks made a little narrower than the mouths of the vessels [so that the cork slides through the neck and drops easily into the vessel] and through the middle of each cork should pass a rod graduated in equal section of three finger-breadths, each clearly marked off from the next. In each section should be written the most evident and ordinary events that occur in war, e.g., on the first, "Cavalry arrived in the country," on the second "Heavy infantry," on the third "Light-armed infantry," next "Infantry and cavalry," next "Ships," next "Corn," and so on until we have entered in all the sections the chief contingencies of which, at the present time, there is a reasonable probability in wartime. Next, he tells us to bore holes in both vessels of exactly the same size, so that they allow exactly the same escape.
Then we are to fill the vessels with water and put on the corks with the rods in them and allow the water to flow through the two apertures. When this is done it is evident that, the conditions being precisely similar, in proportion as the water escapes the two corks will sink and the rods will disappear into the vessels. When by experiment it is seen that the rapidity of escape is in both cases the same, the vessels are to be conveyed to the places in which both parties are to look after the signals and deposited there. Now whenever any of the contingencies written on the rods occurs he tells us to raise a torch and to wait until the corresponding party raises another. When both the torches are clearly visible the signaler is to lower his torch and at once allow the water to escape through the aperture. Whenever, as the corks sink, the contingency you wish to communicate reaches the mouth of the vessel he tells the signaler to raise his torch and the receivers of the signal are to stop the aperture at once and to note which of the messages written on the rods is at the mouth of the vessel. This will be the message delivered, if the apparatus works at the same pace in both cases.
The British civil engineer Francis Whishaw, who later became a principal in the General Telegraph Company, publicized a hydraulic telegraph in 1838 but was unable to deploy it commercially. By applying pressure at a transmitter device connected to a water-filled pipe which travelled all the way to a similar receiver device, he was able to effect a change in the water level which would then indicate coded information to the receiver's operator.
To each end of a column he attaches a float board with an index, and the depression of any given number of figures on one index, will be immediately followed by a corresponding rise of the float board and index at the other end. It is supposed that this simple longitudinal motion can be made to convey all kinds of information. It appears to us that the amount of information which can be conveyed by the motion in one direction only, of the water, or backward and forwards, must be limited. To make the mere motion backwards and forwards of a float board, indicated on a graduated index, convey a great number of words or letters, is the difficulty to be overcome.
The article concluded speculatively that the "... hydraulic telegraph may supersede the semaphore and the galvanic telegraph".
In the 9th century, during the Arab–Byzantine wars, the Byzantine Empire used a system of beacons to transmit messages from the border with the Abbasid Caliphate across Asia Minor to the Byzantine capital, Constantinople.
According to the Byzantine sources (Constantine Porphyrogenitus, Theophanes Continuatus and Symeon Magister), the line of beacons began with the fortress of Loulon, on the northern exit of the Cilician Gates, and continued with Mt. Argaios (identified mostly with Keçikalesı on Hasan Dağı, but also with Erciyes Dağı near Caesarea), Mt. Samos or Isamos (unidentified, probably north of Lake Tatta), the fortress of Aigilon (unidentified, probably south of Dorylaion), Mt. Mamas (unidentified, Constantine Porphyrogenitus has Mysian Olympus instead), Mt. Kyrizos (somewhere between Lake Ascania and the Gulf of Kios, possibly Katerlı Dağı according to W. M. Ramsay), Mt. Mokilos above Pylae on the southern shore of the Gulf of Nicomedia (identified by Ramsay with Samanlı Dağı), Mt. Saint Auxentius south-east of Chalcedon (modern Kayışdağı) and the lighthouse (Pharos) of the Great Palace in Constantinople. This main line was complemented by secondary branches that transmitted the messages to other locations, as well as along the frontier itself.The main line of beacons stretched over some 450 miles (720 km). In the open spaces of central Asia Minor, the stations were placed over 60 miles (97 km) apart, while in Bithynia, with its more broken terrain, the intervals were reduced to ca. 35 miles (56 km). Based on modern experiments, a message could be transmitted the entire length of the line within an hour. The system was reportedly devised in the reign of Emperor Theophilos (ruled 829–842) by Leo the Mathematician, and functioned through two identical water clocks placed at the two terminal stations, Loulon and the Lighthouse. Different messages were assigned to each of twelve hours, so that the lighting of a bonfire on the first beacon on a particular hour signalled a specific event and was transmitted down the line to Constantinople.According to some of the Byzantine chroniclers, the system was disbanded by Theophilos' son and successor, Michael III (r. 842–867) because the sight of the lit beacons and the news of an Arab invasion threatened to distract the people and spoil his performance as one of the charioteers in the Hippodrome races. This tale is usually dismissed by modern scholars as part of a deliberate propaganda campaign by 10th-century sources keen to blacken Michael's image in favour of the succeeding Macedonian dynasty. If indeed there is some element of truth in this report, it may reflect a cutting-back or modification of the system, perhaps due to the receding of the Arab danger during Michael III's reign. The surviving portions of the system or a new but similar one seem to have been reactivated under Manuel I Komnenos (r. 1143–1180).Communications receiver
A communications receiver is a type of radio receiver used as a component of a radio communication link. This is in contrast to a broadcast receiver which is used to receive radio broadcasts. A communication receiver receives parts of the radio spectrum not used for broadcasting, that includes amateur, military, aircraft, marine, and other bands. They are often used with a radio transmitter as part of a two way radio link for shortwave radio or amateur radio communication, although they are also used for shortwave listening.Francis Whishaw
Francis Whishaw (13 July 1804 – October 1856) was an English civil engineer. He was known for his role in the Society of Arts, and as a writer on railways. Later in life he was a promoter of telegraph companies.Henry Sutton (inventor)
Henry Sutton (4 September 1855, Ballarat, Victoria – 28 July 1912) was an Australian designer, engineer, and inventor credited with contributions to early developments in electricity, aviation, wireless communication, photography and telephony.List of Marconi wireless stations
A list of early wireless telegraphy radio stations of the Marconi Wireless Telegraph Co. Guglielmo Marconi developed the first practical radio transmitters and receivers between 1895 and 1901. His company, the Marconi Wireless Telegraph Co, started in 1897, dominated the early radio industry. During the first two decades of the 20th century the Marconi Co. built the first radiotelegraphy communication stations, which were used to communicate with ships at sea and exchange commercial telegram traffic with other countries using Morse code. Many of these have since been preserved as historic places.MCI Communications
MCI Communications Corp. was an American telecommunications company that was instrumental in legal and regulatory changes that led to the breakup of the AT&T monopoly of American telephony and ushered in the competitive long-distance telephone industry. It was headquartered in Washington, D.C.Founded in 1963, it grew to be the second-largest long-distance provider in the U.S. It was purchased by WorldCom in 1998 and became MCI WorldCom, with the name afterwards being shortened to WorldCom in 2000. WorldCom's financial scandals and bankruptcy led that company to change its name in 2003 to MCI Inc.Multiplexing
In telecommunications and computer networks, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource. For example, in telecommunications, several telephone calls may be carried using one wire. Multiplexing originated in telegraphy in the 1870s, and is now widely applied in communications. In telephony, George Owen Squier is credited with the development of telephone carrier multiplexing in 1910.
The multiplexed signal is transmitted over a communication channel such as a cable. The multiplexing divides the capacity of the communication channel into several logical channels, one for each message signal or data stream to be transferred. A reverse process, known as demultiplexing, extracts the original channels on the receiver end.
A device that performs the multiplexing is called a multiplexer (MUX), and a device that performs the reverse process is called a demultiplexer (DEMUX or DMX).
Inverse multiplexing (IMUX) has the opposite aim as multiplexing, namely to break one data stream into several streams, transfer them simultaneously over several communication channels, and recreate the original data stream.NPL network
The NPL Network or NPL Data Communications Network was a local area computer network operated by a team from the National Physical Laboratory in England that pioneered the concept of packet switching. Following a pilot experiment during 1967, elements of the first version of the network, Mark I, became operational during 1969 then fully operational in 1970, and the Mark II version operated from 1973 until 1986. The NPL network, followed by the wide area ARPANET in the United States, were the first two computer networks that implemented packet switching, and were interconnected in the early 1970s. The NPL network was designed and directed by Donald Davies.Optical communication
Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date back several millennia, while the earliest electrical device created to do so was the photophone, invented in 1880.
An optical communication system uses a transmitter, which encodes a message into an optical signal, a channel, which carries the signal to its destination, and a receiver, which reproduces the message from the received optical signal. When electronic equipment is not employed the 'receiver' is a person visually observing and interpreting a signal, which may be either simple (such as the presence of a beacon fire) or complex (such as lights using color codes or flashed in a Morse code sequence).
Free-space optical communication has been deployed in space, while terrestrial forms are naturally limited by geography, weather and the availability of light. This article provides a basic introduction to different forms of optical communication.Rotary dial
A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing. It is used when initiating a telephone call to transmit the destination telephone number to a telephone exchange.
On the rotary phone dial, the digits are arranged in a circular layout so that a finger wheel may be rotated with one finger from the position of each digit to a fixed stop position, implemented by the finger stop, which is a mechanical barrier to prevent further rotation.
When released at the finger stop, the wheel returns to its home position by spring action at a speed regulated by a governor device. During this return rotation, the dial interrupts the direct electrical current of the telephone line (local loop) a specific number of times for each digit and thereby generates electrical pulses which the telephone exchange decodes into each dialed digit. Each of the ten digits is encoded in sequences of up to ten pulses so the method is sometimes called decadic dialling.
The first patent for a rotary dial was granted to Almon Brown Strowger (November 29, 1892) as U.S. Patent 486,909, but the commonly known form with holes in the finger wheel was not introduced until ca. 1904. While used in telephone systems of the independent telephone companies, rotary dial service in the Bell System in the United States was not common until the introduction of the Western Electric model 50AL in 1919.From the 1980s onward, the rotary dial was gradually supplanted by dual-tone multi-frequency push-button dialing, first introduced to the public at the 1962 World's Fair under the trade name "Touch-Tone". Touch-tone technology primarily used a keypad in form of a rectangular array of push-buttons for dialing.Telex
The telex network was a public switched network of teleprinters similar to a telephone network, for the purposes of sending 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.
The "telex" term refers to the network, not the teleprinters; point-to-point teleprinter systems had been in use long before telex exchanges were built in the 1930s. Teleprinters evolved from telegraph systems, and, like the telegraph, they used binary signals, which means that symbols were represented by the presence or absence of a pre-defined level of electric current. This is significantly different from the analog telephone system, which used varying voltages to represent sound. For this reason, telex exchanges were entirely separate from the telephone system, with their own signalling standards, exchanges and system of "telex numbers" (the counterpart of telephone numbers).
Telex provided the first common medium for international record communications using standard signalling techniques and operating criteria as specified by the International Telecommunication Union. Customers on any telex exchange could deliver messages to any other, around the world. To lower line usage, telex messages were normally first encoded onto paper tape and then read into the line as quickly as possible. The system normally delivered information at 50 baud or approximately 66 words per minute, encoded using the International Telegraph Alphabet No. 2. In the last days of the telex networks, end-user equipment was often replaced by modems and phone lines, reducing the telex network to what was effectively a directory service running on the phone network.Voice of Russia
The Voice of Russia (Russian: Голос России, tr. Golos Rossii), commonly abbreviated VOR, was the Russian government's international radio broadcasting service from 1993 until 2014, when it was reorganised as Radio Sputnik. Its interval signal was a chime version of 'Majestic' chorus from the Great Gate of Kiev portion of Pictures at an Exhibition by Mussorgsky.