10. Skim through the text and try to formulate the main idea: The first revolution in mobile phones

When cellular systems began swit­ching from analog to digital transmission in the early 1990s, the main goal was to increase capacity. The systems therefore needed a different kind of voice coding from that employed in wired networks.

Simple pulse code modulation, as intro­duced into wired networks, would not do, for it increased the bandwidth needed to transmit a voice call. No matter-twisted-wire pairs had bandwidth to spare, ren­dered unusable for analog transmission by excessive noise and distortion. Digital tech­nology vanquished those impairments so that the entire bandwidth could carry rev­enue-producing traffic.

The cellular picture is different. Bandwidth really is limited and must be hus­banded. So sophisticated voice-coding tech­niques, implemented in advanced coder-decoders (codecs), compress speech by re­moving some of its natural redundancy. This they do by making all kinds of assump­tions about the voice traffic carried on the radio channel. And they succeed. Whereas the usual wire-line codec converts speech into a 64-kb/s bit stream (8000 eight-bit samples per second), the voice codecs used in cellular services get by with a fifth of that, or even less.

Word – building

1. Here is a list of adjectives for you to memorize. Explain what they mean:

-able: agreeable, amiable, available, capable, considerable, disreputable, indispensable, inevitable. liable, memorable, miserable, probable, remarkable..

-ible: audible, compatible, contemptible, edible, forcible, horrible, illegible, incredible, intelligible, negligible, plausible, possible, terrible, responsible, sensible, visible.

2. Form adjectives from the given verbs and nouns, and explain their meaning. Pay attention to their spelling and pronunciation. Use a dictionary.

Mоdel: to accept - acceptable; to rely - reliable, to conceive - conceivable; to value - valuable.

Note: after с and g the letter e is retained: to notice - noticea­ble; to manage - manageable.

to avoid, to bear, to convert, to suit, to admire, to advise, to compare, to cure, to imagine, to measure, to remove, to change, to exchange, to force, to replace, to trace, to envy, to justify, to pity, to vary.

3. Fill in the blanks with the words given below.

adorable, disagreeable, imaginable, inconceivable, indispens­able, reliable, suitable, unmistakable, valuable.

1. In my opinion she was the most ... of all ladies. 2. They have warned the doctor, guarded their tongues, done everything ...to prevent her from learning the truth. 3. He thought of the ... distance a man travels. 4. I hardly think that she is a very ... person. 5. Presently the child gave a little sigh, very slight, but.... 6. He was looked upon by his superiors as a ... officer. 7. His wrist-watch was a ... thing made by a famous clock-maker. 8. I was astonished to see that ... attic in which she was lying. 9. This dictionary had achieved international recognition as an … practical reference book to English as a foreign language. 10. He shook his head, “It's almost ...I’ll never understand unless you explain.” 11. The look she gave was charged with an ... terror.