Thursday, December 4, 2008
today went sch for a 2 hr de pdpr, nv do any soildering..learn only kmap.Then actually wan to go for dcnt tut de but got to wait for 5 hrs.Wat can i do in 5hr de break in sch?study meh? hahaha..i wont de lor.. with weeli n i, we will just talk non stop n can just forget abt studying.Anyway instead of studying or go for a 5hrs break we 4 went to kfc ad have our lunch.Actually everything was so fine de,BUT ttk la..anyhow talk then weeli angry le.So after that i went studying with wt..LOLS.we end up talking for hrs instead of studying.But i promise that i come home will study my dcnt de..cos tml got test then somemore next thurs will have a coomon test.Sick man.Y must we go for common test?go sch jiu ok le mah..y test n exam.make us so stress.okok..below are some real boring stuff abt wat i am studying.DCNT!
Speed of data transmission is base on
1:available bndwidth of the transmission medium
2:quality of tranmission medium(level of noise)
3:levels of signal to be transmitted.
Nyquist rate=2fmax
Bit RATE = 2 * max transmission freq * number of bits
Guided transmission media=
Optical fibre( among the 3 tis is the best it have fastest bit rate thus it have the largers bandwidth.)
=
Twisted wires =Coaxial cables.HDB3 is not a Polar line coding scheme.
RS-232 is a standard that applies to serial ports.
Data communication uses parity bit becos it can act as an error checking mechanism.
bandwidth= higher freq-lower freq
pulse modulation signal:(got3)
PAM= PULSE AMPLITUDE MODULATION
PWM= PULSE WIDTH MODULATION
PPM=PULSE POSITION MODULATION
Digital modulation methods:
DM=DELTA MODULATION
PCM=PULSE CODE
(got tis wrong during practise)CT mustget it right!!
The sequence of PCM IS: bandlimiting
sampling
quantiziling
ecoding.
Simplex: data tranmission is alway undirectional.receive only
eg: printer
half deplux:both direction but nt the sametime.eg:web document.
full deplux:same time same direction.eg: telephone
effective data communincation:
1-delivery
2-accuary
3-timeliness
hahha i guess tis is wat i all know abt dcnt..guess im gg to fail my test tml..lols
Labels: common test, DCNT, DM, exam, kfc, PAM, PCM., PPM, PWM, ttk, weeli, wt
9:47 PM
