Telecommunications and Control Systems Essentials
Telecommunications
Basic Concepts
1. What elements are always present in communication?
The sender, the message, the receiver, the channel, and the transmission medium.
2. What is a wave?
A wave is a physical phenomenon spreading through space, transporting energy but not matter.
3. What types of waves exist?
Mechanical and electromagnetic waves.
4. What types of waves are used in modern telecommunications?
Electromagnetic waves.
5. What is a periodic wave?
A local disturbance with repeated cycles, such as a sine wave.
6. What is wavelength?
The distance a wave travels to complete one cycle.
7. What is the period of a wave?
The time it takes for a wave to complete one cycle.
8. What is the frequency of a wave?
The inverse of the period; the number of cycles completed per unit of time.
9. What is the speed of propagation of a wave?
The distance a wave travels in a given time.
10. How fast do electromagnetic waves propagate?
They travel at the speed of light (300,000 km/s).
11. Can we know the wavelength of an electromagnetic wave from the frequency?
Yes, because they travel at a constant speed (speed of light).
Transmission and Communication Types
12. What types of communications are transmitted in response to the environment?
Wire transmission and wireless transmission.
13. What kinds of cables are used?
Pair cable, coaxial cable, and fiber optics.
14. What was the first means of modern telecommunications?
The telegraph. It used an electrical circuit between two stations connected by a cable, allowing a switch trigger in one to send a signal to the other.
15. How does the telephone work?
The telephone has two components: the microphone and the earpiece. The microphone converts sound vibrations into electrical signals, and the earpiece converts electrical signals back into sound.
16. What is Morse code?
A code associating each letter of the alphabet with a set of dots and dashes.
17. What is a PBX?
Private Branch Exchange: centers where telephone network circuits are switched to connect two users with a continuous circuit, establishing communication.
18. What does the microphone do on a phone?
It converts sound vibrations into electrical signals.
Modulation and Signal Processing
19. What is modulation?
The combination of the signal containing the audio message with a carrier wave.
20. What types of modulation exist?
Amplitude modulation (AM) and frequency modulation (FM).
21. What is amplitude modulation (AM)?
The amplitude of the carrier wave varies depending on the extent of the message.
22. What is frequency modulation (FM)?
The frequency of the carrier signal varies depending on the message.
23. Why modulate a signal in telecommunications?
To transmit low-frequency signals over long distances using a higher-frequency carrier signal.
24. What is multiplexing in the frequency domain?
Making various communications through the same medium by giving each one a certain frequency range.
25. Does it make sense to modulate a signal transmitted by cable?
No, because the signal arrives at the receiver without losing intensity.
26. What is meant by attenuation of a wave?
The intensity of waves propagating in three-dimensional space is inversely proportional to the square of the distance from the source.
Electromagnetic Spectrum and Applications
27. What is the electromagnetic spectrum?
The energy distribution of all electromagnetic waves.
28. What is a geostationary satellite?
A satellite with a forward speed equal to the Earth’s rotation speed, appearing fixed over a point on Earth.
29. What are VHF and UHF bands used for?
Broadcasting services (FM), mobile communications, TV services, amateur radio, etc.
30. What characteristic of waves in the MF and HF bands is used for long-distance communication?
Reflection by the ionosphere.
Television and Display Technologies
31. What kinds of TV screens are there?
Liquid crystal display (LCD), plasma screens, and cathode ray tube (CRT) screens.
32. What is an LCD screen?
Two layers of glass with a crystalline material that changes transparency with electrical current.
33. What is a CRT screen?
A screen coated with phosphor, emitting light when struck by electrons.
34. What is a plasma screen?
A screen containing an inert gas that produces light when activated by an electric current.
35. How are radio and television similar and different?
Similar in using waves for signal transmission; different in that TV images and sound have a short delay due to complex production.
Additional Concepts
36. What is ionizing radiation?
Radiation with enough energy to ionize matter.
37. What is bandwidth?
The amount of information or data that can be sent via a network connection in a given period.
38. What is GPS?
Global Positioning System: a satellite navigation system to determine the position of an object.
39. What is a transit PBX?
A hub that sends calls to distant locations or other countries.
40. What is a tuner?
A device to tune in a signal frequency.
41. What is a demodulator?
An element that separates the carrier wave from the message.
Control and Robotics
Basic Concepts
42. What is an automatic machine?
Mechanisms that constantly repeat a designed action.
43. What is a control system?
A set of elements that automate a machine.
44. What is a robot?
An automatic, reprogrammable machine that detects and reacts to environmental information.
45. What is the difference between a robot and an automatic machine?
A robot adjusts its action based on stimuli.
46. What is a block diagram?
A scheme representing the steps in a control system.
47. What types of control systems exist?
Open loop and closed loop.
48. What is a comparator?
A device comparing the current state with a setpoint.
49. What is a transducer?
A device transforming physical size into another dimension, usually electrical.
50. What is a sensor?
A device capturing information in the form of physical magnitudes.
51. What is the error signal?
The difference between the setpoint and feedback signal.
52. What is the feedback signal?
Information about the system being controlled.
53. How can a transistor be used in automatic control?
As a switch.
54. What differentiates open loop and closed loop systems?
Open loop systems work automatically without feedback; closed loop systems use sensors to adjust actions.