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).

5. 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.