29-12-2010, 11:33 AM
Submitted by:IshanVerma
[attachment=7725]Introduction
Analog And Digital System
Analog System:
A string tied to a doorknob would be an analog system. They have a value that changes steadily over time and can have any one of an infinite set of values in a range. If you put a measuring stick or ruler at a specific point along the string, you can measure the string's value every so many seconds at that point. When you watch it move, you will see it moves constantly. It doesn't instantly jump up and down the ruler.
Digital System:
A digital system would be to flick the light switch on and off. There's no 'in between' values, unlike our string. If the switch you are using is not a dimmer switch, then the light is either on, or off. In this case, the transmitter is the light bulb, the media is the air, and the receiver is your eye. This would be a digital system.
Analog And Digital Signal
Analog Signal:
An analog signal is any time continuous signal where some time varying feature of the signal is a representation of some other time varying quantity. An analog signal is a datum that changes over time-say, the temperature at a given location; the depth of a certain point in a pond; or the amplitude of the voltage at some node in a circuit.
In analog technology, a wave is recorded or used in its original form. So, for example, in an analog tape recorder, a signal is taken straight from the microphone and laid onto tape. The wave from the microphone is an analog wave, and therefore the wave on the tape is analog as well. That wave on the tape can be read, amplified and sent to a speaker to produce the sound.
In analog signal the value could change between a negative value to positive or from zero to a positive value.
Digital Signal:
It can refer to discrete-time signals that are digitized, or to the waveform signals in a digital system. Digital signals are digital representations of discrete-time signals, which are often derived from analog signals. A discrete-time signal is a sampled version of an analog signal, the value of the datum is noted at fixed intervals (for example, every microsecond) rather than continuously.
In digital technology, the analog wave is sampled at some interval, and then turned into numbers that are stored in the digital device. On a CD, the sampling rate is 44,000 samples per second. So on a CD, there are 44,000 numbers stored per second of music. To hear the music, the numbers are turned into a voltage wave that approximates the original wave.
The digital signal only recognises values at or around 2 points and interprets them as a logic 1 or 0.
Analog Vs. Digital
Digital Advantages:
Digital devices offer several important advantages over their analog counterparts.
• Digital media, including CDs and DVDs, can hold much more data than analog tapes.
• In addition, digital files are easy to copy with perfect fidelity, while succeeding generations of analog copies are slightly different, and slightly degraded, from the source.
• Digital devices may consume less power if they feature fewer moving parts, or may be more accurate, as in the case of clocks.
• They also have a lesser likelihood of mechanical failure than more complex mechanical analog devices.
• Digital communication systems offer much more efficiency, better performance, and much greater flexibility.
• In telecommunication, digital signals have an original blueprint that has to be replicated at the conclusion point of the transmission, therefore it is more accurate and clear than analog signals.
Analog Advantages:
Despite the prevalence of digital devices in the world today, there are still areas where analog devices remain in use.
• Film cameras offer images with a softer quality than digital pictures. Coupled with the lower cost of analog film, this is why most major films are still shot on 35mm film rather than digital video.
• The same is true of audio, although to a much lesser extent; while most of the music industry has gone digital, some music lovers prefer the richness of analog musical recordings rather than compressed digital files.
• Analog devices may also be easier to repair in cases of mechanical failure, while digital devices are subject to computer glitches that require costly replacement.
• Finally, digital devices can be difficult to learn how to use, especially for users who have spent many decades living with more traditional analog technology.
Digital Disadvantages:
• Digital has a few shortcomings. Since devices are constantly translating, coding, and reassembling your voice, you won't get the same rich sound quality as you do with analog.
• Also digital is still relatively expensive.
• Though digital lines carry lower voltages than analog lines, they still pose a threat to your analog equipment.
Analog Disadvantages:
• Analog technology is older and has been used for decades. It is cheap too but the problem with analog signals is that there is a limitation on the size of the data that can be transmitted at any given point of time.
• The primary disadvantage of analog signaling is that any system has noise - i.e., random variation. As the signal is copied and re-copied, or transmitted over long distances, these random variations become dominant.
• Analog signals use continuously variable electric currents and voltages to reproduce data being transmitted. Since data is sent using variable currents in an analog system, it is very difficult to remove noise and wave distortions during the transmission. For this reason, analog signals cannot perform high-quality data transmission.
• The performance of an analog device directly relates to the strength of the signal it receives. As the signal gets worse, so does the display or audio output of the device.