The small size and large information-carrying capacity of optic fibres is much high as compared to copper twisted-pair cables in telephone systems. 2) Continuous passive links more than 100 km long have been produced. With repeaters, messages over thousands of kilometers of fibre can be sent. Because of low losses, separation between repeaters in a … Read more

X-rays cause damage to living tissue. As x-ray photons are absorbed in tissues, they break molecular bonds and create highly reactive free radicals (such as h and oh), which in turn can disturb the molecular structure of the proteins and especially the genetic materials. Young and rapidly moving cells are particularly susceptible; hence x-rays are … Read more

We often hear on radio, TV and read in news papers about peoples on drugs. What these drugs do to individual's life? Many of these substances are given by physicians to prevent or cure pain and diseases. These are drugs of medicinal value and this is proper use of a drug. Morphine, aspirin, sleeping pills … Read more

social service is service and facilities provided to common people by the government or richer people. for example facilities like those of education, medical teatment,free travel free clothing etc. let us see how students can provide social service in different ways. first of all, students can play the educational role in very sucessful manner. they … Read more

students are afraid of examinations for different reasons. first of all, they think that examinations are very difficult. they fear they may not be able to answer most of the questions in their examinations and might fail. but it ofen happens that a student in the examination hall finds his papers to be unexpectedly easy. … Read more

By smoking we usually mean smoking of tobacco. There are many people who are addicted to the smoking of opium and other intoxicating drugs. Tobacco was first brought from America to Europe. The habit of smoking prevails in every part of the world. Most eminent doctors of the world have expressed their opinion about its … Read more

Unemployment is an economic term. Employment means occupation, to be engaged in doing something productive is to be employed. So unemployment means absence of employment. When the people are out of work, they are said to be unemployed. Unemployment is a world-wide problem. Even rich and advanced countries like U.S.A, U.K, and France suffer from … Read more

The dog is a pet animal. It is faithful and useful. It has many varieties. The bull terrier is very furious to look at. The most common pet in our homes is ALASTIAN a large wolf-like dog. The faithfulness of the dog is proverbial and there are many stories about it. The dog is a … Read more

Biomass is a potential source of renewable energy. This includes all the organic materials such as crop residue, natural vegetation, trees, animal dung and sewage. Biomass energy or bio conservations refers to the use of this material as fuel or its conservation into fuels. There are two methods used for the conservation of biomass into … Read more

A covalent bond in which the shared electron pair is unequally attracted by the two bonded atoms is called a polar bond. Usually, a polar covalent bond exists between two unlike atoms. There are some molecules in which the shared electron pair is not equally attracted. For example ,when a covalent bond exists between two … Read more

: "The circulation of free nitrogen from the atmosphere to protein through plants and animals and finally back to atmospheric nitrogen is called nitrogen cycle." The nitrogen cycle consists of a series of reactions of nitrogen and its compounds. Almost all of these reactions take place through living organisms such as green plants and bacteria. … Read more

A solid solution of two or more metals or metals and a non-metal is called an alloy. It is a homogenous mixture of two or more metals. Some alloys also contain carbon and silicon. The physical properties of alloys are generally different from their component elements. Preparations Of alloys : An alloy is usually prepared … Read more

It's a major problem for most of the parents that their kid has started smoking at an age that is not suitable for them. They're complaining that their son has started smoking in early age and it is affecting his health. Their major concern is that they should stop smoking. I conducted a survey in … Read more

Cordless System Operating Environments Residential – a single base station can provide in-house voice and data support Office A single base station can support a small office Multiple base stations in a cellular configuration can support a larger office Telepoint – a base station set up in a public place, such as an airport Residential … Read more

TDD also known as time-compression multiplexing (TCM) Data transmitted in one direction at a time, with transmission between the two directions Simple TDD TDMA TDD Simple TDD Bit stream is divided into equal segments, compressed in time to a higher transmission rate, and transmitted in bursts Effective bits transmitted per second: R = B/2(Tp+Tb+Tg) R … Read more

Analog Signal A continuous representation of a continuous event. An analog connection is one which continuously varies in amplitude and frequency. The amplitude of the signal is representation of its loudness while the frequency represents its tone or pitch. Digital Signal A digital signal is defined at discrete times only represented by fixed states "digits". … Read more

A series of regularly recurring pulses is made to vary in amplitude, duration, shape, or time as a function of the modulating signal Used to transmit both analog and digital information, such as voice and data.The analog signal is sampled, digitized and encoded into a digital pulse stream.If the signal is already is in digital … Read more

Instead of transmitting the exact amplitude of the sampled signal, only certain discrete value closest to the true one is transmitted. At the receiving end the signal value will have a value slightly different from any of the specified discrete steps due to noise and distortions encountered in the transmission channel. If the disturbance is … Read more

Errors occur on every sample except where the sample size exactly coincides the mid-point of the decision level. If smaller steps are taken the quantization error will be less. However, increasing the steps will complicate the coding operation and increase bandwidth requirements. Quantizing noise depends on step size and not on signal amplitude The quantizing … Read more

A reversible process is one which can be retraced in exactly the same order, without producing any change in the surroundings. In the reversible process, the working substances pass through the same stages as in the direct process but thermal and mechanical effects at each stage are exactly reversed. If heat is absorbed in the … Read more