Data Communications Flashcards
What is duplex transmission?
can send and receive data at the same time
What is half duplex transmission?
can receive and send data but only one at a time
how do we send bits over wire?
use different voltages (RS232 uses +15v for 0 and -15v for 1 but only suitable for short distances)
each voltage represents a bit
What are the parts of data Communication?
information source, source de/encoder, de/encryptor, channel de/encoder, de/modulator and physical medium
how do we transmit data over further distances and represent signals?
continuous oscillating signals can go much further distances
how is continuous oscillating signal used by communication systems?
they use it as a carrier for the data then its modulated to represent the bit value
what are the different types of modulation available?
Amplitude, frequency, phase shift
what is a modem?
hardware used to modulate and demodulate the signal
what is digital modulation?
digital signals represent info by fixed set of valid levels e.g 1 and 0
how many bits could we represent at a time from 4 voltage levels?
2 bits at a time
whats the drawback of digital modulation?
system would get more susceptible to noise
what does modulation give us?
symbols
how can symbols be used?
can assign specific bit patterns to each symbol
what happens when we detect that signal?
we can recover those bits assigned to symbols
what do you mean by symbols?
if we had 2 we can assign them 0 and 1
if 4 then 00,01,10,11
