Discussions from ECE
Difference between CDMA & GSM- These are the two different means of mobile communication being presently used world wide. The basic difference lies in the Multiplexing method used in the airial communication i.e. from Mobile Tower to your mobile and vice versa... CDMA uses Code Division Multiple Assess as the name itself indicates, for example you are in a hall occupied with number of people speaking different language. You will find that the one language you are knowing will be heard by you and the others will be treated like noise. In the same manner each CDMA mobile communication takes place with a "code" communicating between them and the other end if one is knowing that code then only it can listen to the data being transmitted i.e. the communication is in the coded form. On the other hand GSM uses Frequency Division Multiplexing in which each user is allocated a particular bandwidth till the communication is taking place.
A transducer is a device, usually electrical, electronic, electro-mechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer. In telecommunication, the term transponder (short-for Transmitter-responder and sometimes abbreviated to XPDR, XPNDR, TPDR or TP) has the following meanings: An automatic device that receives, amplifies, and retransmits a signal on a different frequency (see also broadcast translator). An automatic device that transmits a predetermined message in response to a predefined received signal. A receiver-transmitter that will generate a reply signal upon proper electronic interrogation. A communications satellite?s channels are called transponders, because each is a separate transceiver or repeater.
Crosstalk is a disturbance caused by the electric or magnetic fields of one telecommunication signal affecting a signal in an adjacent circuit. In an telephone circuit, crosstalk can result in your hearing part of a voice conversation from another circuit. The phenomenon that causes crosstalk is called electromagnetic interference (EMI). It can occur in microcircuits within computers and audio equipment as well as within network circuits. The term is also applied to optical signals that interfere with each other.
A photodiode is made to detect light quickly a solar cell is made to collect energy from light. They are both typically silicon diodes, but modified to meet their different requirements. A photodiode has to be fast, which means low capacitance, which means small area of silicon. Therefore, it is not very sensitive, and cannot generate much power from light. A solar cell has as large an area as you can afford to buy, getting watts per square inch. There are other differences in the way they are made, and how the PN junction is grown, but they all relate to this difference in purpose.
There is a limit to how far you can get television signals. The power is spreading out the farther you are away from the source. At some distance, you reach a point where the noise in the atmosphere becomes greater than the signal, and you can no longer extract all the information from the signal. Digital television has much error correction, many bits are sent just so corrections can be made when there are errors. This helps on the fringe, but even this fails when the signal gets weak enough. However, error correction makes the signal perfect until you hit that exact point where the correction fails. Thus, digital TV has a sharp cutoff point - you get a perfect picture, or it goes away completely. Therefore, electromagnetic waves do lose information. Think of someone aiming a flashlight at you. The person walks further and further away from you. At some point, you are just not going to be able to tell. What if there were fogs or lots of pollution in the air? Alternatively, 20 other flashlights and you had to pick out just the one. It is easy and 100% when they are close.
All computer logic today uses FETs as switches. A FET is a switch with gain, meaning that a small signal change on its input (the Gate) causes a bigger signal in the Drain. Bigger does not mean bigger voltage, it usually means more current at the same voltage, so it can drive many other inputs after it. Two FETs can be connected together to make a logic gate, like an AND function. In addition, gates can be connected together to make flip-flops and counters and adders, etc. Logic "1" is usually a higher voltage than logic "0", and logic 0 is usually zero volts. In newer processors, the high voltage is less than a volt, since the FETs are so small that 1.5V will blow them up. Therefore, it is not the presence of a signal or the lack of one; it is a high voltage and a low voltage. There is nothing that the computer translates, that voltage is it, throughout the computer. That is what binary means, one of two voltages. There is no clock involved to make something binary all signals in the computer are all binary logic with a voltage. Even a clock is just a logic signal that goes between 1 and 0 at a periodic rate.
Exact meaning of Manual testing is,testing the software or any application by manually without use of automation tools.
Digital Image Processing refers to the digital manipulation of a picture or video."Photoshopping" is an example of Digital image processing where we can manipulate an image as our wish.Another example is a digital camera in which the picture is captured on an image sensor and is converted to a jpg file to be saved on a memory card. Digital Signal Pocessing is a generic term used for the manipulation of digitally encoded signals like video signals or radio signals.Digital Image processing also included in it because in DIP the digital image signal is transferred from one part of the camera to another part, its done by microprocessors .
The common-mode rejection ratio of a differential amplifier (or other device) measures the tendency of the device to reject input signals common to both input. A high CMRR is important in applications where the signal of interest is represented by a small voltage fluctuation superimposed on a voltage offset, or when relevant information is contained in the voltage difference between two signals. (example-audio transmission over balanced lines.) The CMRR is a very important specification, as it indicates how much of the common-mode signal will appear in your measurement. The value of the CMRR often depends on signal frequency. CMRR is often important in reducing noise on transmission lines.The CMRR of the measurement instrument determines the attenuation applied to the offset or noise. Mathematically, "It is the ratio b/w diffferitial gain to common mode gain"