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what is a digital signal

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ata-ur-rehman

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i got a problem and confused ........ is a signal digital if it is discrete at y-axis but not at x-axis....... i think from the concept of DIGITAL ELECTRONICS it is digital.......or in PCM(Pulse Code Modulation) we use the sample and hold technique and the quantized output is directly converted to binary equalent( without sampling)
 

You are referring to a signal like out put of a D to A converter.

That is discrete in quantity (quantised) but not discrete in time.

And output of a D to A is, technically, analog.
 
I think his question is more fundamental. Most digital signals are ordinary electrical signals that quickly (but not instantaneously) change between two voltages levels. At the receiving device, any voltage higher than a certain threshold voltage is interpreted as "one", anything lower is "zero". That's a simplification -- there are other details such as noise margin, hysteresis, rise time, differential mode, optical instead of electrical, etc.

What does DLD mean? Digital logic device maybe?
 

some definitions for DLD are:

DLD Dense Logic Device
DLD Digital Lifestyle Device
DLD Display List Driver
DLD Distance Learning Directorate

It depends what are you talking about the correct definition.
 

it is not a digital signal, but discret signal
 

artsil23 said:
some definitions for DLD are:

DLD Dense Logic Device
DLD Digital Lifestyle Device
DLD Display List Driver
DLD Distance Learning Directorate

It depends what are you talking about the correct definition.
Click to expand...
DLD IS FOR Digital Logic Design............ if you dont understand it then in simple "Digital ElectronicsS".
 

ata-ur-rehman said:
i got a problem and confused ........ is a signal digital if it is discrete at y-axis but not at x-axis....... i think from the concept of DIGITAL ELECTRONICS it is digital.......or in PCM(Pulse Code Modulation) we use the sample and hold technique and the quantized output is directly converted to binary equalent( without sampling)
Click to expand...
a singnal represented by TWO levEL called DIGITAL SIGNAL
 

discrete signal, discontinuous signal called digital. ex. PCM signal
 

yes it is alright

at x-axis we r having time and it may be our requirement to take it for sampling, changing time, measuring at some specific time, taking readings for some intervals etc.

but when comes to y-axis we have only 2 options 1 or 0
 

if signal is discontinuous in x axis then it is called discrete signal

but IDEAL digital signal is discontinuous in both X and Y axis
 

ISDN line level of +3v +1v –1v –3v represent the digital signals of 2 bit 00, 01, 10, 11
But its is an analog signal

I think signal is digital if it represents only “0” and “1”
 

Ant 2 level signal is digital and a signal taking values between two limits(continuous ) is analog...
 

ata-ur-rehman said:
i got a problem and confused ........ is a signal digital if it is discrete at y-axis but not at x-axis....... i think from the concept of DIGITAL ELECTRONICS it is digital.......or in PCM(Pulse Code Modulation) we use the sample and hold technique and the quantized output is directly converted to binary equalent( without sampling)
Click to expand...

No, not necessarily digital. when you see a Sine wave in X-Y coordiate it is a wave (analog).
when you see it from Z- axis (basic definition of frequency domain) it seems a line (shape like discrete)

Naveed
 

ata-ur-rehman said:
i got a problem and confused ........ is a signal digital if it is discrete at y-axis but not at x-axis....... i think from the concept of DIGITAL ELECTRONICS it is digital.......or in PCM(Pulse Code Modulation) we use the sample and hold technique and the quantized output is directly converted to binary equalent( without sampling)
Click to expand...


Digital signal is abstraction of real analog signal (voltage or current) that continuous in time and changes them value between two different significance.
 

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