datacom_electronics

Question 1

A detectable physical quantity or impulse (as a voltage, or magnetic field strength) by which messages or information can be transmitted.

Answer 1

Signal

Question 2

type of signal that can take only discrete values

Answer 2

digital

Question 3

type of signal that can take values within a continuous range.

Answer 3

analog

Question 4

s will have the same value as that of s at time t
after a time interval T has elapsed.

Answer 4

periodic signal

Question 5

the instantaneous value of a signal in any time. For
electrical the unit is volts.

Answer 5

Amplitude

Question 6

the number of repetitions per unit time.

Answer 6

Frequency

Question 7

used to indicate a relative position and the unit used is the same as that for angles

Answer 7

Phase

Question 8

refers to the amount of time, in seconds, a signal needs to complete one cycle.

Answer 8

period

Question 9

refers to the number of periods in one second.
* F = 1/T and T = 1/F

Answer 9

frequency

Question 10

symbol for amplitude (Sinusoids)

Answer 10

A

Question 11

symbol for time (Sinusoids)

Answer 11

t

Question 12

symbol for phase (Sinusoids)

Answer 12

ϕ

Question 13

symbol for frequency (Sinusoids)

Answer 13

f

Question 14

signal transmission used for digital signals

Answer 14

co-dec (encoder-decoder)

Question 15

signal transmission used for analog signals

Answer 15

mo-dem (modulator-demodulator)

Question 16

4 encoding and modulating techniques

Answer 16

Digital data with digital signals
Digital data with analog signals
Analog data with digital signals
Analog data with analog signals

Question 17

the amount of data in bits per second that is transmitted

Answer 17

Data rate

Question 18

the amount of time it takes for the transmitter to emit a bit (1/data rate).

Answer 18

Duration or length of a bit

Question 19

the rate at which signal level is changed, expressed in units of baud.

Answer 19

Modulation rate

Question 20

0 = low
1 = high

Answer 20

Non Return-to-Zero Level (NRZ-L)

Question 21

0 = no transmission at the beginning of interval
1 = has transition at the beginning of interval

Answer 21

Non Return-to-Zero Inverted (NRZ-I)

Question 22

0 = no line signal
1 = positive or negative level, with successive 1’s alternated

Answer 22

Bipolar - AMI

Question 23

0 = positive or negative level with successive 0’s alternated
1 = no line signal

Answer 23

Pseudoternary

Question 24

0 = transition from high to low at the center of an interval
1 = transition from low to high at the center of an interval

Answer 24

Manchester

Question 25

0 = transition at the beginning of an interval
1 = no transition at the beginning of an interval

There is always a transition at the center of an interval

Answer 25

Differential Manchester

Question 26

Modulating techniques of Digital Data with Analog Signal (3)

Answer 26

Amplitude Shift Keying (ASK)
Frequency Shift Keying (FSK)
Phase Shift Keying (PSK)

Question 27

symbol for amplitude (ASK)

Answer 27

A

Question 28

symbol for digital data input (ASK)

Answer 28

x

Question 29

symbol for carrier frequency (ASK)

Answer 29

fc

Question 30

symbol for carrier phase (ASK)

Answer 30

ϕc

Question 31

formula for Amplitude Shift Keying (ASK)

Answer 31

s(t) = xA cos (2π fc t + ϕc )

Question 32

formula for Frequency Shift Keying (FSK)

Answer 32

s(t) = xA cos (2π f1 t + ϕc ) binary 1
xA cos (2π f2 t + ϕc ) binary 0

Question 33

formula for Phase Shift Keying (FSK)

Answer 33

s(t) = A cos (2π fc t + π ) binary 1
A cos (2π fc t ) binary 0

Question 34

If the reference of a phase shift is with respect to the previous transmitted bit, it is termed as

Answer 34

differential PSK

Question 35

is another form of angle-modulated digital modulation

Answer 35

Quadrature Phase Shift Keying (QPSK)

Question 36

is another technique of converting digital data into analog signals that vary (or shift) both phase and amplitude of the carrier signal.

Answer 36

Quadrature Amplitude Modulation (QAM)