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Flashing, signal, instructions, dashes, steady, acknowledge, relay, code




1. A communication relay is a station that messages between various points, so as to facilitate communications between units. 2. The idea of flashing dots and from a lantern was first put in to practice by Captain, later Vice Admiral, Philip Colomb in 1867. 3. His original, which the Navy used for seven years, was not identical with Morse, but Morse code was eventually adopted with the addition of several special signals. 4. lights were the second generation of signalling in the Royal Navy, after the flag signals. 5. In air traffic control towers,... lamps are still used today, as a backup device in case of a complete failure of an aircraft's radio. 6. Light signals can be red, green or white, and or flashing. 7. Messages are limited to a handful of basic (e.g. "land", "stop" etc.); they are not intended to be used for transmitting messages in Morse code. 8. Aircraft can... signals by rocking their wings or flashing their landing lights.

 

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Greek hydraulic semaphore system involved identical containers on separate hills; 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.

 

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I know it is very difficult to imagine what life must have been like before telephones, text messaging and emails. However, communication between people living in separate cities or states was possible thanks in part to the telegraph machine. The telegraph machine worked by sending a coded message on a wire from one point to another. The most commonly used code was Morse code, which gets its name from inventor Samuel Morse. Morse is credited with perfecting the first telegraph machine in the 1830's. The codes were sent using electrical pulses.

 

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.1. . () . . , . , , . (gunpowder) . : , .

.2. XVIII . 1824 . . 1839 . - 1200 - - . . 30-x XVIII . 15 1855 . - . 1880- .

UNIT 3

TEXT 1. Types of Signals

1. :

convey [kən'veɪ]

quantity ['kwɔntətɪ] ;

spatial ['speɪʃ(ə)l] - ; c

rate [reɪt] - , , , ,

sampling ['sɑːmplɪŋ] [sæ̱m-] - ; ;

fluctuation [flʌkʧu'eɪʃ(ə)n ], [flʌktju'eɪʃ(ə)n]

continuous - ; ;

continuous time

discrete [dɪ'skriːt] ; ;

discrete time

scale [skeɪl] -

decimal ['desɪm(ə)l] -

amplitude ['æmplɪt(j)uːd]

frequency ['friːkwən(t)sɪ]

phase [feɪz] -

sequence ['siːkwən(t)s] ; ;

in sequence - ;

multiplex (adj) ; ,

(n) ; ;

modulate ['mɔdjəleɪt] ;

baseband -

lowpass ()

merge [mɜːʤ] - , ,

train - ,

pulse train -

spectrum ['spektrəm] - ,

bandwidth [bæ̱ndwɪdθ] ,

 

2. :

Communications via electronic means consist of the generation of signals that contain or carry intelligent information and their processing at the receiver to extract this information.

A signal is any kind of physical quantity that conveys information. The examples of signals are audible speech (as it conveys the thoughts (information) of one person to another through the physical medium of sound) or hand gestures (conveying information by means of light). In the field of communications, a signal is generally a relationship of a spatial parameter, such as amplitude, to time. This relationship can be discrete or continuous. A continuous signal or a continuous-time signal is one that has a value defined at every instant. A discrete signal or a discrete-time signal is represented by a time series consisting of a sequence of quantities. Discrete signals are usually received by acquiring values of a continuous-time signal at constant or variable rate - this process is called sampling, or by recording the number of events of a given kind over finite time periods (for example, the ancient Egyptian records of the Nile's yearly floods or the modern histograms of daily currency fluctuations).

An analog signal typically varies continuously over time, while digital signals are present at discrete points in time. A well-known example of analog vs. digital is that of clocks: analog being the type with pointers that slowly rotate around a circular scale, and digital being the type with decimal number displays or a "second-hand" that jerks rather than smoothly rotates. An analog clock is capable of indicating every possible time of a day. In contrast, a digital clock is capable of representing only a finite number of times (every tenth of a second, for example).

Most signals in nature are analog. Sound, noise, light, heat, and electronic communication signals going through air (or space) are examples of analog signals. The most fundamental analog signal is the periodic sine wave. Its three main characteristics are its amplitude (the size of the waveform), frequency (the number of cycles per second that the wave undergoes) and phase (the position of a point in time (instant) on a waveform cycle, while a complete cycle is defined as 360 degrees of phase).

A common digital signal configuration is the binary waveform represented by a sequence of two types of pulses of known shape. The information contained in a digital signal is given by the particular sequence of the presence (a binary, or logic, one) or absence (a binary zero) of these pulses. These are known as bits (this word was derived from binary digits).

 

 





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