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Digital transmission is preferred because it does not need to be reproduced accurately. An analog waveform after passing through several amplifiers in a long call. done correctly. This is enough to differentiate 0 from 1. This property has made digital transmission more reliable than analog. This alsoCheap and easy to maintain.
In short, the telephone system consists of three main components:
1. Local loop (analog twisted pairs go to homes and businesses).
2. Trunks (digital fiber optics that connect changing offices).
3. Transfer Office (calls will be transferred from one trunk to another).
After a brief examination into the politics of the telephone, we will return to each of these three components.
some details. Local loops give everyone access to the entire system, so they are important. unexpectedly
They are the weakest link in the system. For long distance trunks, the main issue is how to aggregate multiple issues
Simultaneous call and send in the same fiber. This topic is called multiplexing and we will study three
There are various ways of doing this. In the end, there are two different ways to make a difference; We will see both. Visit
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For the decades before 1984, the Bell System provided local and long-term support throughout the region.
United States of america. In the 1970s, the US federal government believed it was an illegal monopoly.
accused of breaking On January 1, 1984, AT&T broke away from the AT&T long lines and won.
23 BOC (Bell Operating Company), and several pieces. 23 BOC was divided into seven regions
BOC (RBOC) so they live according to the economy. The Absolute Nature of Telecommunications in the United States
Changed overnight by court order (not active in Congress).
The so-called MFJ (Revised Final Judgment, an oxymoron). If anything – if the verdict can be reversed, it is clearly not final). This event led to an increase. Competitiveness, better service and shorter distances for consumers and businesses. However, the prices. Local service increased as cross-subsidy was removed from long-distance calling and local service was required.
Be independent. Many countries have now started similar competition. To clarify who can do what, USA 164 LATA (Local Access and traffic area). More difficult, a LATA is like an area covered by an area code. inside a can,
LEC (Local Transaction Carrier), which has a monopoly on traditional telephone service. Parts are the most important LEC BOC, although some CANs have one or more Independent telephone companies acting as LECs.
All transit between LATA is handled by a different type of company, an IXC (IntereXchange Carrier). First, AT&T Long Lines Is the Only Serious IXC, But Now WorldCom and Sprint Are Solid Rivals ixc business. Ensuring that all IXCs are treated equally is one of the degenerative concerns. The quality of taxes, fees and the number of digits their customers have to dial in order to use them.
Let’s start with the area most people are familiar with: the two-wire local ring from the phone. The decision of corporate offices in homes and small businesses. The local ring is often referred to as the “final”. miles,” the length can be up to several miles. It has been using analog signals for over 100 years and This is likely to continue in the coming years due to the high cost of converting to digital. However, change is also taking place in the last palace of analog transmission. In this part we will study.
Traditional local loops and new developments take place here, especially with an emphasis on data
Communication from home computer. If you want to send digital data to the computer’s analog dial-up queue, you must first convert the data. Analog form for transmission in the local ring. This change is done by a device called a modem, We will study soon. The data is converted into digital form at the telephone company’s office end
Transfer to perennial trunks.
If the computer has another terminal modem, the reverse transition—from digital to analog—must be overcome.
Local ring to target. This configuration is ISP 1 (Internet Service Provider), As with a bank of modems, each is connected to a separate local loop. This ISP Can Handle A Lot connection because it contains modems (assuming that the server or its servers have sufficient system power). This Adjustment is normal until the 56-kbps modem appears, for obvious reasons.
An analog signal transmission consists of varying voltages representing a stream of information over time. if delivery
If the media is correct, the receiver will receive the same signal sent by the transmitter. unexpectedly The media is not perfect, so the received signal is not equal to the transmitted signal. For digital data, it is
Differences can lead to mistakes. Transmission lines are affected by three main problems: damping, deflection delay and noise. is quenching Loss of energy due to signal propagation. Losses are expressed in decibels per kilometer. respect The energy lost depends on the frequency. To see the effect of maintaining this frequency, don’t think of it as a signal.
Simple waveform, but a series of Fourier elements. Each component is reduced to a different amount,
A distinct Fourier spectrum is generated in the receiver. To make matters worse, different Fourier elements also propagate at different speeds on the wire. This Due to the difference in velocity, the signal received at the other end gets distorted. Another problem is noise, which doesn’t want power from sources other than the transmitter. VU ALL EDU SUBJECTS PAST PAPERS, VU ALL EDU SUBJECTS PAST PAPERS, VU ALL EDU SUBJECTS PAST PAPERS, VU ALL EDU SUBJECTS PAST PAPERS, VU ALL EDU SUBJECTS PAST PAPERS, VU ALL EDU SUBJECTS PAST PAPERS, VU ALL EDU SUBJECTS PAST PAPERS, VU ALL EDU SUBJECTS PAST PAPERS, VU ALL EDU SUBJECTS PAST PAPERS, VU ALL EDU SUBJECTS PAST PAPERS, VU ALL EDU SUBJECTS PAST PAPERS, VU ALL EDU SUBJECTS PAST PAPERS,