Wi-Fi is the trade mark of the Wi-Fi Alliance and the brand name of products using the IEEE 801.11 family of standards and not the short form of Wireless Fidelity as most of us think. Wi-Fi simply represents the trade mark of IEEE 802.11x. Wi-Fi is the technology that allows an electronic device to transfer data wirelessly using radio waves. It is the WLAN ( Wireless Local Area Network) used in home, office, educational institutions etc to provide wireless networking for the internet access. The common Wi-Fi activated systems like Computer, Mobile phone etc can be connected to the internet wirelessly through the Wi-Fi system. For this, the computer should have a wireless network interface controller called Station. The access point of Wi-Fi- is called Hot spot and may be a wireless Router or Modem. The Wi-Fi usually has a range of 20 meters in indoor applications. The technology of Wi-Fi came into action during 1985.
Computer Mouse ( Computing Mouse) is the input device of the computer which is a pointing device that detects the two dimensional motion relative to its supporting surface. The mouse has two or three buttons, to control the desktop screen and to provide various commands to the PC. The mouse sometime has a wheel to perform system dependent operations. The motion of the mouse is translated into the motion of the pointer on the display which controls the Graphical User Interface (GUI). Old type mouse has a ball to move on the surface but modern optical mouse uses reflected light to activate the circuitry inside. The Optical mouse has one or more Red LED and a Photodiode detector to accept the reflected light from the LED. The Photodiode detects the mouse movement relative to the underlying surface such as mouse pad or table top. In some mouse, laser is used instead of LED. The driver communicate the mouse movements in standard units called “Mickeys”
Stethoscope is a medical diagnostic tool for Auscultation which is the listening of internal sounds of the body. Auscultation is used to examine the heart sounds, breath sounds, bowel sounds etc. Auscultation requires skill, clinical experience and a good quality stethoscope. An experienced physician can distinguish normal Lub and Dub sounds of the heart as well as heart murmurs and gallops. In combination with the sphygmomanometer, the Stethoscope is used to measure the blood pressure. The Stethoscope was invented by Rene Laennec of France in 1816. The two-sided stethoscope was invented by Rappaport and Sprague in the early 20th century.
The Sphygmomanometer is the diagnostic device used to measure the blood pressure. Blood pressure is the pressure exerted by the blood on the wall of the artery during its flow. It is meant for keeping constant blood flow throughout the body irrespective of the position. Normal blood pressure is 80 mmHg-120 mmHg in which 80 mmHg is the diastolic pressure when the heart relaxed and 120 mmHg is the systolic pressure when the heart contracts. The diastolic pressure up to 90 mmHg and systolic pressure up to 130 mmHg is treated as normal but the person is in the border line of Hypertension. Usually a BP index is used since the BP may vary slightly depending on the conditions of the body and either systolic or diastolic pressure may be high as in the case of aging. Even if we sit in front of the Physician, our BP may increase slightly due to nervousness, a condition called as “White coat effect”. BP index is calculated by adding systolic and diastolic pressures and then dividing by 2. In normal case it is 120+80 / 2 = 100. Up to 110 is treated as normal. BP measurement on both the arms and periodic measurement are advisable to confirm the Hypertension before going on medication.
Conventional Sphygmomanometer is mercury column based and has an inflatable cuff to restrict the blood flow. It is used in conjunction with Stethoscope to hear the sound during the measurement. Sphygmomanometer was invented by Samuel Siegfried Karl Ritter von Basch in 1881.
Electrocardiograph is the Medical diagnostic instrument used to record the electrical activities of the heart. It gives a recorded data in the form of a graph called ElectroCardioGram or ECG. Human heart functions through the electrical impulses produced by the specialized groups of cells called Pace makers (SA node and AV node) located on the right surface of the heart. The electrical signals generated by the pace makers will be available on the surface of skin also. The Electrocardiograph detects these signals and output as a graph. By observing the waveform, it is easy to confirm the variations in the functioning of heart.
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MRI Scanner is the Medical Imaging device used to image the soft parts of the body especially the Brain. Magnetic Resonance Imaging or MRI is the technique used in MRI scanner to provide the detailed structure of the brain. Unlike CT (Computed Tomography) scanning, MRI uses no ionizing radiation but uses powerful magnetic field to align the nuclear magnetization of hydrogen atoms in the water content of the body. Diseased tissue, such as tumors, can be detected because the protons in different tissues return to their equilibrium state at different rates. By changing the parameters on the scanner ,this effect is used to create contrast between different types of body tissue.Patients with some metal implants, cochlear implants, and cardiac pacemakers are prevented from having an MRI scan due to effects of the strong magnetic field and powerful radio frequency pulses.
The common AC tester is the simplest form of tool to test the presence of AC in the mains wiring. The Screwdriver type AC tester has a Neon lamp inside which glows when the current passes from the mains wiring to the ground through the user’s body. It uses the stray capacitance of the body to complete the circuit.
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