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Analog and Digital Signals Compared

written by: Vandana Singhal • edited by: Lamar Stonecypher • updated: 11/29/2010

Digital technology has replaced analog technology in most electronic devices. It is simply because digital signals are more easily transmitted as compared to analog signals. This article explains the difference between analog and digital signaling.

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    Casio f91w digital watch   Digital watches in the early 1970s became a craze among consumers due to the simplicity of their operation and ease of use compared to analog watches. Today’s CDs are based upon the digital technology while older vinyl records were analog. Though analog devices are still in use, digital systems are used wherever possible.

    Image: Wikipedia Commons, Geo Swan

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    Difference between Analog and Digital

    An analog system uses the waveforms as it is in its original form while a digital system uses discrete values- electrical voltages. A digital system converts the original waveforms into a set of numbers and records these numbers. At the time of operations, this system converts these numbers into a voltage stream that closely resembles the original analog wave form.

    Discrete values in the digital system are represented by number or some non-numeric symbols such as icons or symbols. It makes use of discrete values for processing, transmission, input, storage or display, instead of a continuous range of values as in the analog system. In the digital system, data signals are converted into binary format and audio or video data is represented by a series of ones and zeros.

    Analog technology and digital technology differ at all levels especially in the method of signal input, the storage of data, and the signal transmission, or you can say that the internal working of the device components differs.

    digital analog  

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    The major difference between digital and analog transmission is the transmission capacity or the bandwidth required for each system. For example, for an average NTSC video signal, analog signals can work on a very low bandwidth of about 4.5 MHz having a data rate of 143.2 Mb/s. At the same time, a digital video transmission may require a large bandwidth of about 74.25 MHz with a 1485 Mb/s data rate. For digital transmissions, advanced single-mode optical fiber can easily make these higher data rates accessible for longer distances while conventional copper coax cannot perform at these levels of data rates at all.

    One more important difference between the digital and analog transmission is the device’s ability to recover the transmitted signal. In case of analog systems, to reconstruct the transmitted signal at the receiver end, some adjustment is required. This is because analog modulation is variable in behavior. At this point, you can judge the simplicity of digital system as it used binary format to encode the signals which can be easily reconstructed. Digital signals can include larger information that allows any transmission error to be corrected at the receiver’s end. It makes digital transmission systems better over analog since they can eliminate the effect of noise.

    Digital technology makes use of sampling to record, transmit and reconstruct the data. For instance, when a digital music system records the original waveform, it samples the music at a rate of thousands times per second. It is about 44,000 times per second for a CD recording. It means it records 44,000 numbers per second. The more the number of sampling per second, the better will be the quality of the signals. At the time of reconstruction, original waveforms are produced at a rate of one bit at a time at lightning speed.

    A digital system delivers the reconstructed signals as the exact copy of the original signals without any disturbance and noise.

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