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what is Printer/ define         After a document is created on the computer, it can be sent to a printer for a hard copy (printout). Same printers offers special features such as coloured and large page formats. Some of the most commonly used printers are: 1.       Laser Printer 2.         Dot Printer 3.       Ink Jet Printer 4.       Line Printer Laser Printer: A laser printer produces high quality print that one normally finds in publishing. It is extremely fast and quiet. Moreover, the operation of a laser printer is extremely easy with automatic paper loading and no smudging or messing up of ink ribbons. Most laser printers output 6 to 12 pages per minute. Minimum buffer memory in a laser printer is 1 MB. Dot Matrix Printer: The dot matrix printer (DMP, in short) is a very versatile and inexpensive output device and is suitable for most of our computing jobs. In a DMP the print head physically “hits” the paper through the ribbon and produces text (or im

What is Modem and Fax Modem: A modem enables your computer your computer to receive/send data from/to remote places through telephone lines, to the other computer provided each has a compatible modem. These are attached to serial port of the computer. Modems are used to connect a computer to a remote network through dial-up or leased line connections. A modem is controlled by using a communication program. Some of the On-line services, one can avail through a modem, are: “Electronics mail” “Banking and travel reservations” “File transfers” “Fax Services” “Internet access” Modem of varying speeds, measurable in Megabits per second (Mbps), are available in the market. Some of the common speeds are 14.4 Mbps, 28.8 Mbps, 33.7 Mbps and 56.4 Mbps. Fax: In the present day computer system, FAX machines can be attached with A COMPUTER IS SEND AND RECEIVE DOCUMENTS CREATED IN THE COMPUTER TO DISTANT PLACES, BRINGING COMPUTERS AND COMMUNICATION toget

Important Laws on Environment 1.       The Indian Boilers Act, 1923 2.       The Indian Forests Act, 1927 3.       The factories Act, 1948 4.       The Radiation Protection Rules, 1971 5.       The Motor Vehicle Act, 1938, amended in 1988 6.       Environmental Impact Assessment Notification, 1994 7.       Eco Mark Notification, 1997 8.       Environmental Audit Notification, 1997 9.       Public Hearing Notification, 1997 10.   Coastal Zone Management authority, 1998 11.   Biodiversity Protection Act, 2002 12.   The National Environment Tribunal Act, 1992 13.   The Energy Conversation Act, 2001  

What is Ionosphere? The ionized region of the earth’s upper atmosphere extending from about 40 km to the height of a few earth radii above the surface of the earth, is referred to as the ionosphere. The ionosphere is made up of electrons, and positive and negative ions in the background of neutral particles of the atmosphere. The concentration of the neutral particles is much greater than that of the charged species, so that the ionosphere is a weakly ionized medium.  The direct interactions of the atmospheric constituents, such as oxygen and nitrogen, with X-ray and ultraviolet radiation from the sun produce electrons and positive ions simultaneously in the ionosphere . A few electrons that are so produced, adhere to the neighbouring neutral particles to create negative ions. Also some electrons recombined with neighbouring positive ions to reproduce the original neutral particles. In this way the generation and the loss of electrons and ions in the ionosphere occur si

           Propagation of Radio waves Radio waves launched from a transmitting antenna travel outward and are not markedly affected by the surrounding atmosphere, rain, snow etc. These waves readily pass through nonmetallic substances but are greatly attenuated by metals. Their movement in free space is best, and no material medium is required for their propagation. Electromagnetic waves with frequencies extending from about 10 kHz to 300 GHz are classed as radio waves. These wave are subdivided into smaller ranges for convenience, as shown in Band -- Frequency range -- wavelength range – Principle of application Very low frequency (VLF) – 10 to 30 kHz – 30 to 10 km – Direct long range communication Low frequency (LF) – 30 to 300 kHz – 10 to 1 km – Marine, navigational aids Medium frequency (MF) – 300 kHz to 3 MHz – 1km to 100m – Broadcasting High frequency (HF) – 3 to 30 MHz – 100 to 10m – all types of communication Very high frequency (VHF) – 30 to 300 MHz

What is Input Devices? Input devices accept data and instructions from the user. Following are the examples of various input devices, which are connected to the computer to provide input. There are many input devices. Some important input devices are as follows: 1.       Keyboard 2.       Mouse 3.       Joystick 4.       Light Pen 5.       Optical/magnetic Scanner 6.       Touch Screen 7.       Microphone for voice as input 8.       Track Ball 1.       Keyboard: A keyboard is the most common input device now. Several kinds of keyboards are available, but they resemble each other with minor variations. The keyboard in most common use is the QWRTY board (from keys Q, W, E, R, T, Y in the top left corner of the keyboard). IBM and IBM compatible PCs or microcomputers use 104 keyboard; so called since it has 104 keys. In these keyboards, the cursor control keys are duplicated to allow easier use of the numeric pad. 2.       Mouse: A mouse is an electro-m

What is Satellite Communication? For sky wave propagation, usually the frequency band extending from 3 to 30 MHz is employed. Radio links over long distance over the earth surface can be established by multi-hop transmission. But reliable communication by means of sky waves is hampered due to problems like fading, ionospheric disturbance and storms. Artificial satellite offer reliable communication links over long distance. An artificial satellite is hurled into space in a circular orbit in the equatorial plane at height of 36000 km above the surface of the earth.  The period of revolution of the satellite round the earth is 24 hours, i.e., equal to the period of rotation of the earth about in own axis. So, to an observer on the earth’s surface, the satellite appears to be stationary. Such satellite are therefore referred to a geostationary satellite and the orbit as the synchronous orbit.  The wave containing information is transmitted to the satellite from a transmit