 |
|
Discontinuous, or digital signals
Modulation refers to the process of converting digital signals into analog form so that data can be sent over the phone lines. Demodulation is the process of converting the analog signals back into digital form so that the receiving computer can process them. The hardware that performs modulation and demodulation is called a modem (modulate/demodulate). The sending computer must be connected to a modem that modulates the transmitted data, while the receiving computer must be connected to a modem to demodulate the data. Both modems are also connected to the telephone lines.
Exercises:
1. Give Russian equivalents of the following phrases:
Continuous sound waves; could be compared; water coming out of a garden hose; can also differ, these signals are discontinuous; transmitted in patterns of digital signals; a series of ‘on’ and ‘off ‘electrical pulses; the process of converting digital signals.
2. Say if the following sentences are true or false.
1. When we song, we transmit continuous sound waves, or analog signals, that form what we call ‘voice’. 2. Telephone lines aren’t currently an analog communications medium. 3. These signals are discontinuous (discrete) pulses over a transmission medium. 4.Modulation doesn’t refer to the process of converting digital signals into analog form so that data can be sent over the phone lines. 5.Demodulation isn’t the process of converting the analog signals back into digital form so that the receiving computer can process them.
3. Insert missing words, use the text’s vocabulary:
1. Analog signals could be … to a steady stream of water coming out of a garden hose. 2. These signals repeat a certain number of times over a certain time period- their frequency, which is measured in cycles per second, or … . 3. For data to travel from one … to … across the phone lines, the sending computer’s digital data must be converted into analog across the phone lines. 4.… refers to the process of converting digital signals into analog form so that data can be sent over the phone lines. 5. The … computer must be connected to a modem that modulates the transmitted data.
4. Translate these sentences into your native language:
1. Analog signals could be compared to a steady stream of water coming out of a garden hose. 2. Sometimes our voice sound high (composed of high-frequency sound waves) and sometimes our voices sound low (composed of low-frequency waves). 3.Demodulation is the process of converting the analog signals back into digital form so that the receiving computer can process them. 4. The hardware that performs modulation and demodulation is called a modem (modulate/demodulate).
Retell the text.
Text 2
Telephone lines
Words and word combinations:
Unsheathed copper wires – не обшитые медные провода
to string – вешать
to secure – защищать
uninsulated – неизолированный
electromagnetic interference – электромагнитные помехи
twisted – скрученный
garbled – искаженный
susceptible – восприимчивый, чувствительный
digital signals – цифровые сигналы
an amplifier – усилитель
repeaters – трансляционный усилитель
more advanced media – более передовые средства
The earliest type of telephone line was referred to as open wire – unsheathed copper wires strung on the telephone poles and secured by glass insulators. Because it was uninsulated, this type of telephone line was highly susceptible to electromagnetic interference; the wires had to be spaced about 12 inches apart to minimize the problem. Although open wire can still be found in a few places, it has almost entirely been replaced with cable and other types of communications media. Cable is insulated wire. Insulated pairs of wires twisted around each other- called twisted-pair cable- can be packed into bundles of a thousand or more pairs. These wide-diameter cables are commonly used as telephone lines today and are often found in large buildings and under city streets. Even through this type of line is a major improvement over open wire, it still has many limitations. Twisted-pair cable is susceptible to a variety of types of electrical interference (noise), which limits the practical distance that data can be transmitted without being garbled. (To be received intact, digital signals must be ‘refreshed’ every one to two miles through the use of an amplifier and related circuits, which together are called repeaters. Although repeaters do increase the signal strength, which tends to weaken over long distances, they can be very expensive.) twisted-pair cable has been used for years for voice and data transmission; however, never, more advanced media are replacing it.
Exercises:
1. Give Russian equivalents of the following phrases:
Unsheathed copper wires; highly susceptible; electromagnetic interference; communications media; insulated wire; related circuits; signal strength; long distances.
2. Say if the following sentences are true or false.
1. The earliest type of telephone line was referred to as open wire – sheathed copper wires strung on the telephone poles and secured by glass insulators. 2. Although open wire can’t be found in a few places, it has almost entirely been replaced with cable and other types of communications media. 3. These wide-diameter cables aren’t commonly used as telephone lines today and are often found in large buildings and under city streets. 4. Twisted-pair cable is susceptible to a variety of types of electrical interference (noise), which limits the practical distance that data can be transmitted without being garbled. 5. Cable is insulated wire.
3. Insert missing words, use the text’s vocabulary:
1. Although … can still be found in a few places, it has almost entirely been replaced with cable and other types of communications media. 2. Insulated pairs of wires … around each other- called twisted-pair cable- can be packed into bundles of a thousand or more pairs. 3. Twisted-pair cable is susceptible to a variety of types of electrical interference (noise). 4. Digital signals must be ‘refreshed’ every one to two miles through the use of an amplifier and related circuits. 5. Although … do increase the signal strength.
4. Translate these sentences into your native language:
1. Because it was uninsulated, this type of telephone line was highly susceptible to electromagnetic interference; the wires had to be spaced about 12 inches apart to minimize the problem. 2. These wide-diameter cables are commonly used as telephone lines today. 3. Twisted-pair cable is susceptible to a variety of types of electrical interference (noise), which limits the practical distance that data can be transmitted without being garbled. 4. To be received intact, digital signals must be ‘refreshed’ every one to two miles through the use of an amplifier and related circuits, which together are called repeaters.
Retell the text.
Text 3
Cables
Words and word combinations:
An insulated bundle – изолированная связка
threadlike fibers – нитевидные волокна
electric current – электрический ток
to distribute – распределять
to transmit – передавать
electronic devices – электронные устройства
intercontinental – межконтинентальный
fiber-optic cables – оптико-волоконные кабели
widespread – широко распространенный
artificial satellites – искусственные спутники
radio waves – радио волны
practical means – удобные средства
Cable, in electricity and communications, is an insulated bundle of wires or threadlike fibers that carry electric current or pulses of light. Cables are widely used to distribute electric power and to transmit communications signals. They are also used to connect parts of computers and other electronic devices. Electric cables range from intercontinental underwater cables that carry an electric current as small as one-thousandth of a watt to roadside electric lines that are capable of carrying thousands of watts of electricity. Fiber-optic cables transmit communications signals in the form of pulses of light.
Cables came into widespread use in the second half of the 1800’s, when telegraphs and telephones became common. Since the mid-1900’s, communications systems that use radio signals broadcast from transmitters on earth or in artificial satellites have begun to replace some cables. For example, telephone companies now use radio waves to carry most long-distance telephone calls. Communications satellites send television programs and other electronic messages throughout the world. In many cases, however, cables still provide the most practical means of communication.
Exercises:
1. Give Russian equivalents of the following phrases:
Threadlike fibers; electric current; pulses of light; communications signals; connect parts of computers; electronic devices; underwater cables; roadside electric lines; long-distance telephone calls; communications satellites
2. Say if the following sentences are true or false.
1. Cables are narrow used to distribute electric power and to transmit communications signals. 2. Fiber-optic cables transmit communications signals in the form of electromagnetic waves. 3. Cables came into widespread use in the second half of the 1800’s, when telegraphs and telephones became common. 4. Telephone companies now don’t use radio waves to carry most long-distance telephone calls. 5. Communications satellites send television programs and other electronic messages throughout the space..
3. Insert missing words, use the text’s vocabulary:
1. Cable, in electricity and communications, is an insulated bundle of wires or threadlike fibers that carry … … or pulses of light. 2. They are also used to connect parts of … and other electronic devices. 3. Electric cables range from … underwater cables that carry an electric current as small as one-thousandth of a watt to … electric lines that are capable of carrying thousands of watts of electricity. 4. Cables came into … use in the second half of the 1800’s, when telegraphs and telephones became common. 5. In many cases, however, cables still … the most practical means of communication.
4. Translate these sentences into your native language:
1. Cables are widely used to distribute electric power and to transmit communications signals. 2. Electric cables range from intercontinental underwater cables that carry an electric current as small as one-thousandth of a watt to roadside electric lines that are capable of carrying thousands of watts of electricity. 3. Since the mid-1900’s, communications systems that use radio signals broadcast from transmitters on earth or in artificial satellites have begun to replace some cables. 4. Communications satellites send television programs and other electronic messages throughout the world.
Retell the text.
Text 4