Other Flashcards
What is telecommunications:
Sending, receiving and storing information
What information can be used in telecommunications:
Sound, images and data
How is the information transported in telecommunications:
Wires, radio waves or optical fibres
What types of data can be used in telecommunications;
Analogue and digital
What do analogue signals convey:
Sound, light or temperature information
Are analogue signals continuous or discontinuous:
Continuous
Analogue signals can be converted to:
Electrical signals
How are analogue signals transported:
Copper wire or radio waves (has to be converted)
What do digital waves convey:
0 and 1
Are digital signals continuous or discontinuous:
Discontinuous
How are digital signals transported:
Electrical signals, radio waves or optical fibres
How are digital signals better than analogue signals:
No loss of quality and more information
Define attenuation:
When a signal loses strength as it travels
What does amplification do to an analogue signal:
Makes it louder but also increases the attenuation
Why doesn’t amplification affect digital signals:
It does, but the signal can be regenerated so the end signal has the same quality as the original
What are some examples of analogue signals:
Video tapes and vinyl records
What are some examples of digital signals:
CDs and DVDs
What are optic fibres:
Strands of glass the width of a human hair that can be bent
What do optic fibres do:
They reflect light internally - this happens 6000 times per metre at almost the speed of light, and s single strand can carry signals for 12000 phone calls at once by staggering them
Other pros of optic fibres:
Cheaper than copper, thin, light, no interference, signals don’t weaken and they’re more secure
What are the two types of multiplexing:
Time and wavelength division
What is time division multiplexing:
When the signals are sent at different times
What is wavelength division multiplexing:
When the signals are sent at different wavelengths
What is a transmitter:
A machine that turns sound waves to oscillating current to radio waves - a receiver does the opposite
What Hz are ground waves:
<3MHz
What Hz are sky waves:
3-30MHz
What Hz are micro waves:
> 30MHz
What are ground waves:
Waves that travel along the surface of the earth
What are sky waves:
Waves that bounce off the atmosphere
What are micro waves:
Waves that pass through the atmosphere to a satellite that sends them back down again
What is Wi-Fi:
Uses the internet instead of wires
What Hz is Wi-Fi:
2.4GHz
What range does Wi-Fi have:
~100m
Pros of Wi-Fi:
Low cost, convenient, fast, secure, reliable, easy to install, carry lots of data, fewer cables (so less cost to make)
