Vocabulary

2.2 Complete the vocabulary (term) log, i.e. find out definition, part of speech, translation, synonyms and antonyms if possible, decode abbreviations.

Grammar

2.3 Put the verb into the correct form, past perfect or past simple:

1. Therefore, about 2.5 billion years___________ (to pass) on the earth when life (to originate). 2. The Wright Brothers _______(to launch) their plane at Kitty Hawk before Bell___________ (to develop) his own flying machine. 3. Bell ________ (to patent) his telephone first. 4. Bell__________ (to regard) the photo phone as the greatest invention he____________ (to make). 5. By the end of the XX century a satellite of the planet Pluto____________ (to discover). 6. It_____ (to happen) before they_____________ (to connect) the telephone. 7. When we___________ (to come in) he_____________ (to dial already) the number. 8. The samples ________ to vary) in quality but were generally acceptable. 9. We__________ (to wash) our hands before we___________ (to handle) food. 10. He__________ (to show) the ticket which he__________ (to buy) earlier.

Comprehension Check

2.4 Make up no less than 10 questions.

2.5 Read the following text and write a summary to it (no less than 7 sentences) in Russian and English.

Text 2 Telephone

In a conventional telephone system, the caller is connected to the person he wants to talk to by the switches at various exchanges. The switches form an electrical connection between the two users and the setting of these switches is determined electronically when the caller dials the number based upon either pulses or tones made by the caller's telephone. Once the connection is made, the caller's voice is transformed to an electrical signal using a small microphone in the telephone's receiver. This electrical signal is then sent through various switches in the network to the user at the other end where it transformed back into sound waves by a speaker for that person to hear. This person also has a separate electrical connection between him and the caller, which allows him to talk back.

Today, the fixed-line telephone systems in most residential homes are analogue — that is the speaker's voice directly determines the amplitude of the signal's voltage. However although short-distance calls may be handled from end-to-end as analogue signals, increasingly telephone service providers are transparently converting signals to digital before converting them back to analogue for reception. The advantage being that digitized voice data can travel side-by-side with data from the Internet and those digital signals can be perfectly reproduced in long distance communication as opposed to analogue signals, which are inevitably impacted by noise.

Mobile phones have had a significant impact on telephone networks. Mobile phone subscriptions now outnumber fixed-line subscriptions in many markets. There have also been dramatic changes in telephone communication behind the scenes. Starting with the operation of TAT -8 in 1988, the 1990s saw the widespread adoption of systems based upon optic fibers. The benefit of communicating with optic fibers is that they offer a drastic increase in data capacity. TAT-8 itself was able to carry 10 times as many telephone calls as the last copper cable laid at that time and today's optic fiber cables are able to carry 25 times as many telephone calls as TAT-8. This drastic increase in data capacity is due to several factors. First, optic fibers are physically much smaller than competing technologies. Second, they do not suffer from crosstalk, which means several hundred of them can be easily bundled together in a single cable. Lastly, improvements in multiplexing have led to an exponential growth in the data capacity of a single fiber.

Assisting communication across these networks is a protocol known as Asynchronous Transfer Mode (ATM) that allows the side-by-side data transmission mentioned in the first paragraph. The importance of the ATM protocol is chiefly in its notion of establishing pathways for data through the network and associating a traffic contract with these pathways. The traffic contract is essentially an agreement between the client and the network about how the network is to handle the data, if the network cannot meet the conditions of the traffic contract it does not accept the connection. This is important, because telephone calls can negotiate a contract to guarantee themselves a constant bit rate, something that will ensure a caller's voice is not delayed in parts or cut-off completely. There are competitors to ATM, such as Multiprotocol Label Switching (MPLS) that perform a similar task and are expected to supplant ATM in the future. However, this has not yet happened.

Unit 3 Video

3.1 Read and translate the text. Use a dictionary to help you.

Text 1 Digital Video

With digital video, we are able to take two of our senses, sight and sound, convert the analog signals, and combine them in the digital realm. By converting our analog world into the digital realm, we can more easily manipulate sight and sound.

Our vision is inherently analog based. To convert that analog world to a digital one, we need a device to sample analog signals and convert them into the digital domain. This is done using a Charged Coupled Device (CCD). A CCD performs sampling and outputs digital information. Once an image is captured, raw video is converted to more efficient formats that can be manipulated, transported, and stored. In order for businesses to take advantage of the benefits of digital video and to make digital video applications more affordable to implement, numerous compression techniques have been developed. Video compression methodologies take the original, raw video data and shrink it using methods that can either restore the video back to its original state called lossless compression when uncompressed or to a close approximation to the original called loss compression.

Historically, video transmission (synchronous video with audio) was accomplished using traditional analog communication techniques over a coaxial cable physical infrastructure. For both residential and business environments, this typically means supporting overlay networks. In addition to the added costs associated with designing, implementing, and maintaining separate networks, video networks have become increasingly complex as the size of the video network increases. Once the video signal (synchronous video with audio) has been digitized, transporting this signal over a communications network based on standard networking technologies like ATM and Ethernet/IP becomes much easier and cost effective for most businesses and even residential video service delivery. However, due to the latency requirements for video signals, the supporting network infrastructure must exhibit several key characteristics discussed below.

One of the most difficult tasks is to determine the level of video quality that is adequate and required for a certain need. Needs range from video conferencing in a business environment to video surveillance in a public safety environment, to broadcasting for entertainment purposes. The trade-off surrounds quality versus cost, and it centers on the level of video quality necessary to achieve the desired level of realism from the video transmission. These decisions cover the range of digital video solution components above discussed. Cameras, viewing devices, compression methods, and appropriate network infrastructure must be designed and selected to ensure that your video will meet users’ expectations.

Regarding the network infrastructure segment of the overall digital video solution, latency is the main issue. Latency in networking is the amount of time it takes a packet to travel from source to destination. Together, latency and bandwidth define the speed and capacity of a network. In order to address the latency requirements of high-quality digital video transmission, a network based on ATM provides the best solution on the market today. ATM is an International Telecommunications Union - Telecommunication Standardization Sector (ITU-T) standard for cell relay. Cells are the basic unit of transferring data in an ATM network. It is fixed sized and contains destination information and payload. Since the cells are of fixed size, exacting algorithms have been invented to ensure that when data is sent, it will arrive at the appropriate destination intact, with minimal jitter. This trait is better known as Quality of Service (QoS). Today, ATM is the accepted standard technology for video networking. While there are many IP video solutions available on the market today, only ATM can provide the necessary features to support video transmission flawlessly. Since video is very loss and jitter sensitive, ATM QoS guarantees video transmissions will arrive at the destination address intact.

Another main attribute necessary for digital video transmission is network reliability. Network reliability affects latency. In the event of a network outage due to an equipment failure or physical layer problem, the network supporting digital video transmission must be robust enough to identify the outage point and re-route traffic so no interruption in service is noticed by the users. Digital video networks based on ATM technology have an inherent advantage over Ethernet-based networks due to a robust, hierarchical routing protocol called Private Network to Network Interface (PNNI). Network infrastructures leveraging PNNI technology have the proven ability to re-route traffic within 50ms of an outage. This more than supports the latency requirements of digital video. Conversely, IP/Ethernet networks based on RIP and OSPF routing protocols can take up to 30 seconds to re-route traffic due to an outage. This delay will result in unacceptable video service interruptions. Finally, ATM technology has been widely accepted as the network technology of choice in every telecommunication service provider’s network.