analog vs digital

This page on analog vs digital describes difference between analog and digital.

Analog and digital terms refers to continuous and discrete respectively. These terms are used in data communication to represent data and signals to be transmitted or to be received to/from the channel.

In a simple terms, analog describes any waveform(voltage signal,current signal) which is continuous in time and which will have continuous set of amplitude values. This signal can be fed to the oscilloscope to view its variation over time including amplitude/magnitude. Similarly digital signal is nothing but discrete time domain version of the analog signal, which will have sequence of values.

Let us understand difference between them w.r.t. the data. Analog data will have continuous amplitude over time,referred as CACT(Continuous Amplitude Continuous Time). For example, voice and video will have intensity varying continuously with time. Digital data will have discrete values over disctere time instant, referred as DADT(Discrete Amplitude Discrete Time). For example, text and integers are digital form of information. ADC(Analog to Digital converter) is used to convert analog to digital data. DAC(Digital to Analog converter) is used to convert digital to analog data.

Let us assume sine wave with following equation:
x(t)= sin(2 pi fo t)
The same signal in digital discrete form can be represented by following equation
x(n)=sin(2 pi fo n ts)
Where n is the time index ranging from 0,1,2,...etc
and ts is the time period.

A analog signal can be represented by continuous E-M (Electro-Magnetic ) waves which are propagated over co-axial cable,twisted pair,fiber optic or wireless medium based on need. A digital signals are in the form of binary 1 and 0 pulses which are transmitted over copper wires but at short distances.To transmit over long distances either repeater or amplifier devices are to be used so that shape of the information will not get altered or they need to be converted to the analog form to meet the propagation channel requirements.

Analog data are encoded with the use of codec to produce digital bit stream of data. While digital data are encoded with the use of modem to produce analog waveform.


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