--- title: "Communication system and block diagram" subject: "Basic Electronics Engineering" chapter: 5 key: "semester_2/basic_electronics_engineering:comm-system-block-diagram" source: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/comm-system-block-diagram site: BCT Engineering --- # Communication system and block diagram Basic Electronics Engineering · Chapter 5: Communication System - Asked in: 2073 Bhadra, 2+3 marks; 2071 Bhadra, 2+3 marks; 2068 Bhadra, 2+4 marks; 2072 Magh, 2+4 marks; 2073 Magh, 6 marks; 2069 Bhadra, 4 marks; 2068 Magh, 5 marks (asked 7 times) - Video: [Communication system (Block diagram, Basics, Working, Details & Signal Propagation) Explained](https://www.youtube.com/watch?v=kAs8OerKRmc) — Engineering Funda - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/comm-system-block-diagram - Whole chapter: https://www.bctengineer.com/md/semester_2/basic_electronics_engineering/chapter-5 ## Question Define communication system. Draw and explain the block diagram of a communication system (explain each block briefly). ## Short answer A communication system transfers information from a source to a destination through a channel. The input transducer converts the message to an electrical signal; the transmitter modulates and amplifies it; the channel is the physical medium with added noise; the receiver demodulates and amplifies; and the output transducer converts it back to the original form. ## Answer A **communication system** is a system that transfers information (voice, data, video) from one point (source) to another point (destination) through a medium called a channel. #### Block diagram ```text +--------+ +--------+ +-----------+ +---------+ |Informa-|->| Input |->|Transmitter|->| Channel | |tion src| |transd. | |(modulator)| |(medium) | +--------+ +--------+ +-----------+ +----+----+ noise ->| +--------+ +--------+ +-----------+ v |Destina-|<-|Output |<-| Receiver |<-------+ |tion | |transd. | |(demodul.) | +--------+ +--------+ +-----------+ ``` #### Function of each block 1. **Information source:** produces the message, such as voice, music, picture or data. 2. **Input transducer:** converts the message into an electrical signal, for example a microphone converts sound to a voltage. 3. **Transmitter:** processes the signal for sending. It includes amplification, filtering and modulation, which shifts the signal to a high carrier frequency. The signal is then fed to the antenna or line. 4. **Channel:** the physical path between transmitter and receiver. It may be wired (twisted pair, coaxial cable, optical fiber) or wireless (free space). The signal is weakened and distorted here. 5. **Noise:** unwanted signals added in the channel and the equipment, which reduce the signal quality. 6. **Receiver:** receives the weak signal, amplifies it, selects the wanted channel (tuning), and recovers the original message by demodulation. 7. **Output transducer:** converts the electrical signal back to the original form, for example a loudspeaker. 8. **Destination:** the user who receives the message. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is a communication system? A. A system that only amplifies signals B. A system that stores information C. A system that converts ac to dc D. A system that transfers information from a source to a destination through a channel Answer: D. It carries voice, data or video between points via a channel. (Key point: Definition) 2. What does the transmitter do? A. Converts the signal back to sound B. Amplifies, filters and modulates the signal onto a high-frequency carrier C. Adds noise D. Selects the wanted station and demodulates Answer: B. Transmitter processing includes modulation to a carrier before the antenna or line. (Key point: Transmitter) 3. What is noise in a communication system? A. The wanted message B. The carrier wave C. A part of the receiver tuner D. Unwanted signals added in the channel and equipment that reduce quality Answer: D. Noise degrades signal quality. (Key point: Noise) 4. What does the receiver do? A. Modulates the message B. Amplifies, tunes the wanted channel and recovers the message by demodulation C. Converts sound to electrical signal D. Generates the carrier Answer: B. The receiver reverses the transmitter operations. 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