Question

Explain briefly the following terms used in communication systems:
(a) Modulation and (b) Transducer

Answer 1

(a) Communication system is a system which transfers or shares the desired information. The information can be messages, codes, audios, videos, signals, etc. While sharing this information there might be some interference of other informatory signals which will lead to noises in the signals and the information may get lost. By allotting a frequency bandwidth to the signal, the other signals cannot interfere with our signal, thus preventing noises. Think of various alterations that can be applied to a signal to make it unique.
(b) For large distances, a particular information cannot be shared in its actual physical form, it needs to be shared in such a form that it travels a large distance. Modulators and demodulators are used to convey the information, but these modulators and demodulators work only with electrical signals. Think that what if we have such a device that converts a particular form of signal, say sound wave, into electric signals.

Complete step by step solution:
(a) Modulation:
The waveform is a periodic function of time and is called the carrier signal. The alterations in the carrier signal are brought in accordance with a signal called the modulating signal. The modulating signal contains all the information which we want to be transmitted. The information includes the amplitude, frequency, phase, etc. Most of the modulation is carried on radio waves, optics and networks.
There are different types of modulation methods such as Amplitude Modulation (AM), Frequency Modulation (FM), Phase Modulation (PM), etc.
Amplitude Modulation (AM): The amplitude of the carrier signal is changed in accordance with the intensity of the modulating voltage. The frequency of the modulating signal is lower than the carrier signal. In AM, the frequency does not vary.
Frequency Modulation (FM): The frequency of the carrier signal is changed in accordance to the instantaneous value of the modulating signal. In FM, the amplitude does not vary.
Phase Modulation (PM): The phase of the carrier signal is changed in accordance with the amplitude of the modulating signal.
(b) Transducer:
A transducer is a device used to convert the form of energy. Examples of transducers are speakers, microphones, electric generator, solar cell, pencil cell, etc. The transducers deal with energies such as mechanical, light, chemical, heat/thermal, electrical, etc.
Consider a microphone, it converts the sound into electrical signals, alters the signal into audio signals at the output of the speaker. Another example is a thermocouple, it converts the temperature difference into voltage.
The qualities of a transducer depend on the specifications such as range and noise. The range is the ratio of the largest amplitude and smallest amplitude. The noise is unwanted information in a signal.

Note:
(a) As we know that the energy of a wave is proportional to its frequency, in order to travel large distances, the frequency of the carrier wave must be high. The carrier wave can be of different types. It can be continuous or discontinuous (pulse). Also, remember that the signal which contains the information to be transferred is the modulating signal and the one which is used to convey the information is the carrier wave.
(b) Not all transducers can produce an electrical output, these are called passive transducers. The one which are used to produce electrical signals are the active transducers.