encoding and decoding (1 Viewer)

[Liminality]

hey guys, i need a bit of help with this analog data to analog signal, digital signal to analog data stuff.. and can someone please explain PCM?

 

[Embrisa]

I'm also unsire about the coding/decoding stuff, but no-one wants to help. lol. And what does PCM stand for?

 

[Liminality]

it stands for pulse code modulation.. and i dunno anything else =p

 

[JayWalker]

Happy to help:

Analog to Digital: A method of this is PCM. Takes sample measurements 8000 er second of analog data. Each measurement records the volage or the amplitude of the analog signal. The height of curve is divided into 128 different levels, each represented by a 7 bit binary number. Now its digital!

Digital to Analog: Digital data is all 1's and 0's. There are three ways:
-Amplitude modulation: Varies the height of the signal to show a 1 and a 0. Only reliable up to speeds of 1KBps [SLOWWW]
-Frequency modulation: Uses a higher frequency for 1 and a lower frequency for 0. This is more tolerant of noisly lines.
-Phase modulation: changes phase of the signal cycle, where there is a change from a 1 to a 0.

This creates an analogue wave by forming lots of 1's and 0's

 

[Lwaxana]

Comm systems use both analog and digital. For this reason it is often necessary to encode and decode signals.
4 possible processes
AnData to AnSig eg Telephone conversation. system encodes speech and transmits it from sender to receiver.
DigData to AnSig makes it easy for humans to understand. requires encoding of 0s and 1s. telephone system uses modem
DigData to DigSig one computer on a network can communicate with another
AnData to DigSig. analog encoded into series of 0s and 1s by dividing data into 2 groups across a arbitrary line. High group is 1s and low groups 0s. this is called demodulation. Decoding will reverse the process.

 

[Liminality]

wow thanx guys, that helped a lot