# Analog Communications Questions and Answers – PWM

«
»

This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “PWM”.

1. What is the full form of SONET?
a) Synchronous Optical Network
b) Standard Optical Network
c) Secret Optical Network
d) Service Optical Network

Explanation: SONET stands for Synchronous Optical Network. SONET transfers multiple digital bit streams in a synchronized way over optical fiber using lasers.

2. VFO stands for ________
a) Voltage Feedback Oscillator
b) Variable Feedback Oscillator
c) Voltage Frequency Oscillator
d) Variable Frequency Oscillator

Explanation: VFO stands for Variable Frequency Oscillator. VFO is an oscillator whose frequency can be tuned over some range. It is a necessary component in any tunable radio. It is mostly used in superheterodyne receivers.

3. What is used in Hartley oscillator?
a) a piezoelectric crystal
b) two resistor divider
c) a two-capacitor divider
d) a tapped inductor

Explanation: In Hartley oscillator, the oscillation frequency is determined by a tuned circuit consisting of capacitors and inductors. Thus, it is an LC oscillator whose frequency can be varied. Hartley oscillator was invented in 1915.

4. The conditions for sinusoidal oscillation from an amplifier are called _________
a) Loop-gain criteria
b) Hartley criteria
c) Biasing criteria
d) Barkhausen criteria

Explanation: The conditions for sinusoidal oscillation from an amplifier are called Barkhausen criteria. It was invented in 1921.

5. Which parts of a sinusoidal carrier can be modulated?
a) only amplitude
b) only frequency
c) its amplitude, frequency and direction
d) its amplitude, frequency and phase angle

Explanation: If the carrier wave is sinusoidal, then we can vary its amplitude, frequency, and phase in proportion with the wave which is transmitted.

6. The power density of a flicker noise is _________
a) low at high frequencies
b) greater at low frequencies
c) greater at high frequencies
d) low at low frequencies

Explanation: Flicker noise is a form of noise that exhibits an inverse frequency power density curve. It usually occurs at low frequencies. Its power density is greater at low frequencies.

7. Power above the minimum required by an optical receiver is called ________
a) phase margin
b) system margin
c) excess gain
d) gain margin

Explanation: System margin is the term used when the applied power is above the minimum required power by an optical receiver.

8. What is the full form of DWDM?
a) Dense Wavelength Division Multiplexing
b) Dense Wavelength Division Modulation
c) Directed Wavelength Division Multiplexing
d) Directed Wavelength Division Modulation

Explanation: DWDM stands for Dense Wavelength Division Multiplexing. In DWDM, each signal has its own separated wavelength.

9. FTTC stands for ________
a) Fiber To The Curb
b) Fiber Telephone Transmission Cable
c) Fiber Transmission Timing Cable
d) Fiber Telephone Timing Cable

Explanation: FTTC stands for Fiber To The Curb. It is a replacement of Plain Old Telephone Service (POTS) that we see in our neighborhood.