Communication System

Amplitude modulation is

• Change in amplitude of the carrier according to modulating signal

• Change in frequency of the carrier according to modulating signal

• Change in amplitude of the modulating signal according to carrier signal

• Change in amplitude of the carrier according to modulating signal frequency

The graph shows the frequency spectrum of an AM radio wave carrying an audio signal of a single frequency. Determine the frequency of the audio signal.

• 1kHz

• 3 kHz

• 5 kHz

• 7 kHz

An analogue signal is sampled at a frequency of 5.0 kHz. Each sample is converted into a four-bit number and transmitted as a digital signal. Show in which number equal to code 0110.

• 2

• 4

• 6

• 8

The Y-input terminals of a cathode-ray oscilloscope (c.r.o.) are connected to a supply of amplitude 5.0V and frequency 50Hz. The time-base is set at 10ms per division and the Y- gain at 5.0V per division.

Which trace is obtained?

• 
• 
• 
• 

Determine the maximum frequency of the transmitted audio signal

• 18 kHz

• 9 kHz

• 918 kHz

• 909 kHz

Energy loss in wire because of ...

• electrical heating

• absorption

• scattering

To send a message from one person, thing, or place to another is an example of

• decoding.
• receiving.
• transmitting.
• storing.

The person who originates the message is the ...

• Receiver 
• Decoder
• Source
• Encoder

VHF is a abbreviation for what 

• vast help frequencies
• very high frequencies 
• very hot food 
• very helpful frequencies 

What is the point of a repeater 

• To say the message for a seconf time
• turn high power signals into low power signals 
• top turn lower power signals into higher power signals 
• just to add a extra step in transmitting