# digital & discrete signal

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#### KAZIMRAZA

##### Newbie level 3 I would like to understand the diffrence between a discrete and a digital input or out put signal, like 0 and 1 are the states of digital signal similarly how we can diffrenciate between discrete and digital signals

thanks
KAZIMRAZA

#### the_edge

##### Full Member level 3 Digital 101010101010101011100. It is actualy analog because it is defined all the time...

Discrete: Output of some sampling circuit.
They have values at specific times. ### KAZIMRAZA

Points: 2

#### sivakumar_tumma

##### Full Member level 4 KAZIMRAZA said:
I would like to understand the diffrence between a discrete and a digital input or out put signal, like 0 and 1 are the states of digital signal similarly how we can diffrenciate between discrete and digital signals

thanks
KAZIMRAZA

I think , digital signal have the standard values of voltages for 1 and 0.
discrete dont have voltage levels, only smaples it has.....

tell me if I am wrong....

#### maharshi_qis

##### Full Member level 5 discrete signal means it is discrete in only in time but continuous in amplitude..but digital signal is discrete in both time and amplitude..ok.

#### SKS

##### Junior Member level 3 I too have this confusion as :
Modern digital and Analog communication by B.P.Lathi says
>>continuous time and discrete time tells whether the signal is defined for all time or for discrete values of time, respectively.
>>Analog and Digital tell only about the values that a signal can take, i.e finite or infinite.
So the book has given 4 categories of signals:
>>Analog, cont. time
>>Digital, "
>>Analog, Discrete time
>>Digital, "
And it has given the figures also....

BUT!!!!
the book of DSP by Proakis says:
>>Analog signal is continuous in amplitude as well as time...
>>Digita signal is discrete in amplitude as well as time..

Which one is correct??

#### dqhuy

##### Junior Member level 3 digital signal: discrete in time and level.

So digital signal is discrete signal.
Discrete signal is digital signal, this is not always true.

#### jsps

##### Member level 3 discrete signal is discrete in time but continuous is amplitidute, sampled speech signal is discrete signal.
whereas output of any digital circuit is digital having either 0 or 5 V and also discrete in time.

#### The Joy of Electronics

##### Member level 4 As was very well explained above, discrete signals can asume continues values in fixed time points, while digital signals only assume 0 or 1.

#### engr_najam

##### Full Member level 2 discrete signal is discrete in time but continuous is amplitidute, sampled speech signal is discrete signal.
whereas while in digital we can have only fix number of levels in amplitude, e.g 2, 4, 8, etc

#### sonal

##### Banned Digital signals are digital representations of discrete-time signals, which are often derived from analog signals.

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—that can be represented as a mathematical function, with time as the free variable (abscissa) and the signal itself as the dependent variable (ordinate). 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.

A discrete signal or discrete-time signal is a time series, perhaps a signal that has been sampled from a continuous-time signal. Unlike a continuous-time signal, a discrete-time signal is not a function of a continuous-time argument, but is a sequence of quantities; that is, a function over a domain of discrete integers. Each value in the sequence is called a sample.

When a discrete-time signal is a sequence corresponding to uniformly spaced times, it has an associated sampling rate; the sampling rate is not apparent in the data sequence, so may be associated as a separate data item.

#### jetset

##### Full Member level 3 Ok this is statistics, if you go to the root meaning of what discrete is, you will find that a set of discrete values are just a set of meassures taken at different times. The time is not discrete because you can take meassuremnts at the time you want, usually in electronics this time is periodic, but it does not mean that the time is discrete because you can use also variable sampling rate as well. But the values of this meassures has to be made discrete acording to some set of amplitued values. That means a discrete signal is just discrete in amplitude, not in time, because you can take meassures at the time you want, but this meassures can not take intermediate values among a table of amplitude samples.
Digital is just a type of representation of the amplitudes. Usually in electronics we use digital representation because we use digital systems. You can make this representation in numbers at different basis binary(10), hex(00-ff), decimal(0-9), but still digital.

#### afroman

##### Newbie level 5 Discrete signal is a signal written in this form D amplitude belongs to R. and it is not defined allover the time. T could be constant or variable

Discrete signal is a signal written in this form D amplitude belongs to R. and it is not defined allover the time. T could be constant or variable

#### saubhik

##### Full Member level 3 Digital signal means where signal state can only be varied in between the two states '0' and '1' , not in their mid or any other states .

Discrete signal means the signal which is the result of any sampled signal( with respect to time ).

digital signal may or may not be continuous in time scale , i.i it may be Continuous time Digital signal and Discrete time digital signal .

but discrete signal must always be discontinuous with time but have any state .

#### Kral KAZIMRAZA,
Part of the confusion regarding the word "discrete" is that it is used in two different contexts, one context for DSP, and the other context for single bit control signals.
.
In DSP, the word "discrete" (an adjective) for an independent variable (usually time) means that the quantitity is only defined for specific values of the independent variable (time) and is undefined for other values. For the dependent variable, "discrete" (an adjective) means that the value is quantized, and can only take on specific values. Example: For a 4 bit system, the dependent variable can only take on the (possibly weighted) values of 0, 1, 2, 3.
.
In single bit control signals, the word discrete (a noun) is used to define a signal that takes on one of two values (possibly with a tolerance on each value). The two values are continuous variables, that is to say, for each state, the value is defined for all values of time. The value of the discrete can change at any point in time.
Regards,
Kral

#### mkhan

##### Full Member level 3 Hi,

Very simple, a digital signal can have values 0 or 1 but at all times (i.e. at integer values of time or fractions does not matter, e.g. at t = 1 or at t = 1.5) BUT a discrete signal has value only at integer value of time (i.e. it will have value at t = 1 but u can not define it for t = 1.5).

The diagram in first reply of ur question explain this very well.

BR,

MAK

#### Electronica

##### Full Member level 2 discrete signals basically are the middle stage of A/D conversion

#### barmak

##### Member level 4 simple! digatal signals are binary expresion of a discrete number

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