Chapter 13 — Network Cabling: Exercise Solutions Guide
How to Use This Page
1. Attempt every exercise question on your own first — write your answer before looking here. 2. Compare your answer with the solution provided; focus on the reasoning, not just the final choice. 3. Re-read the Key Concepts section for a quick recap before exams. 4. Check the Common Mistakes section to avoid frequent errors that cost marks.
Key Concepts (Quick Recap)
- Transmission media are divided into guided (wired) and unguided (wireless).
- Twisted pair cable — pairs of insulated copper wires twisted together; comes as UTP (unshielded) and STP (shielded). Used for Ethernet LANs. Maximum range ~100 m without repeater.
- Coaxial cable — central copper conductor surrounded by insulation, metallic braid, and outer jacket. Used for cable TV and broadband. Types: Thinnet (RG-58, ~185 m) and Thicknet (RG-11, ~500 m).
- Fibre optic cable — transmits data as light pulses through glass/plastic fibres. Single-mode (laser, long distance) and multi-mode (LED, shorter distance). Highest bandwidth and speed.
- RJ-45 connector — 8-pin connector for twisted pair Ethernet cables.
- BNC connector — Bayonet Neill-Concelman connector used with thin coaxial cables.
- SC/ST connectors — push-pull (SC) and twist-lock (ST) connectors used with fibre optic cables.
- Radio waves — omnidirectional, used for AM/FM radio, cellular networks, Wi-Fi.
- Microwaves — directional, line-of-sight transmission; used in satellite and terrestrial links.
- Infrared — short-range, line-of-sight, cannot penetrate walls; used in TV remotes, IrDA ports.
- Satellite communication — uses a satellite as a relay; covers large areas (footprint); introduces propagation delay.
- Wireless media advantages — mobility, no cabling cost, easy deployment; disadvantages — security risks, interference, lower speed than fibre.
I. Choose the Best Answer (MCQs)
1. Which cable type uses light pulses for data transmission? (a) Twisted pair (b) Coaxial cable (c) Fibre optic cable (d) Ribbon cable
Answer(c) Fibre optic cable Explanation: Fibre optic cables transmit data as pulses of light through glass or plastic fibres, achieving the highest speeds among all cable types.
2. The RJ-45 connector is used with which type of cable? (a) Coaxial cable (b) Fibre optic cable (c) Twisted pair cable (d) Ribbon cable
Answer(c) Twisted pair cable Explanation: RJ-45 is an 8-pin connector standard for Ethernet twisted pair cables (Cat5, Cat5e, Cat6).
3. Which cable is most immune to electromagnetic interference? (a) UTP (b) STP (c) Coaxial (d) Fibre optic
Answer(d) Fibre optic Explanation: Fibre optic uses light, not electrical signals, so electromagnetic interference has no effect on data transmission.
4. The maximum segment length of Thinnet (RG-58) coaxial cable is approximately: (a) 100 m (b) 185 m (c) 500 m (d) 2000 m
Answer(b) 185 m Explanation: Thinnet (10Base2) coaxial cable supports a maximum segment length of about 185 metres.
5. Which wireless medium requires line-of-sight and is used for short-range communication? (a) Radio wave (b) Microwave (c) Infrared (d) Satellite
Answer(c) Infrared Explanation: Infrared communication is short-range and requires line of sight; it cannot pass through walls or obstacles.
6. BNC connector is associated with: (a) Twisted pair cable (b) Thin coaxial cable (c) Fibre optic cable (d) Ribbon cable
Answer(b) Thin coaxial cable Explanation: BNC (Bayonet Neill-Concelman) connectors are used with thin coaxial Ethernet cables (10Base2).
7. Which type of fibre optic cable uses a laser as the light source? (a) Multi-mode fibre (b) Single-mode fibre (c) Step-index fibre (d) Plastic fibre
Answer(b) Single-mode fibre Explanation: Single-mode fibre uses a laser light source and a very thin core (8-10 microns), enabling long-distance, high-bandwidth transmission.
8. UTP stands for: (a) Universal Twisted Pair (b) Unshielded Twisted Pair (c) Unified Transmission Protocol (d) Unbound Twisted Pair
Answer(b) Unshielded Twisted Pair Explanation: UTP stands for Unshielded Twisted Pair — copper wire pairs twisted together without additional metallic shielding.
9. Satellite communication introduces: (a) No delay (b) Low delay (c) Propagation delay (d) Data loss
Answer(c) Propagation delay Explanation: Because signals must travel to a satellite in orbit (typically 35,786 km for geostationary) and back, satellite links have noticeable propagation delay (~270 ms round trip).
10. Which cable category supports Gigabit Ethernet up to 100 m? (a) Cat3 (b) Cat5 (c) Cat5e (d) Cat1
Answer(c) Cat5e Explanation: Cat5e (enhanced Category 5) supports Gigabit Ethernet (1000BASE-T) at distances up to 100 metres.
II. Fill in the Blanks
1. The two types of twisted pair cable are UTP and STP. 2. Fibre optic cable transmits data using light pulses through glass or plastic fibres. 3. The connector used with thin coaxial cable is the BNC connector. 4. SC and ST are common connectors used with fibre optic cables. 5. Infrared transmission requires a direct line-of-sight between sender and receiver. 6. The maximum segment length of Thicknet (RG-11) coaxial cable is about 500 metres. 7. Radio waves are omnidirectional and can penetrate buildings, making them suitable for Wi-Fi and cellular communication. 8. Single-mode fibre uses a laser as the light source and has a smaller core diameter. 9. The process of twisting wires in a twisted pair cable reduces electromagnetic interference (crosstalk). 10. A transceiver converts between the electrical signals of the network device and the light signals in fibre optics.
III. True or False
1. Fibre optic cable is affected by electromagnetic interference.
AnswerFalse Fibre optic uses light signals, not electrical, so it is immune to EMI. 2. UTP cables are cheaper than STP cables. — True. UTP lacks the additional metallic shielding found in STP, making it less expensive. 3. Microwave transmission can pass through buildings. — False. Microwaves require line of sight and cannot pass through buildings or dense obstacles. 4. RJ-45 is an 8-pin connector used in Ethernet networks. — True. RJ-45 has 8 pins and is the standard connector for Ethernet twisted pair cables. 5. Coaxial cable has a higher bandwidth than fibre optic cable. — False. Fibre optic cable has significantly higher bandwidth than coaxial cable. 6. Infrared signals can penetrate walls. — False. Infrared cannot pass through walls or opaque obstacles; it requires a clear line of sight. 7. Satellite communication covers a large geographical area called a footprint. — True. A satellite's footprint is the area on Earth where its signal can be received. 8. STP cables provide better noise protection than UTP cables. — True. The metallic shield in STP reduces external electromagnetic interference. 9. Thicknet uses RJ-45 connectors. — False. Thicknet (10Base5) uses AUI (Attachment Unit Interface) or vampire tap connectors, not RJ-45. 10. Wireless media are more secure than wired media. — False. Wireless signals can be intercepted more easily than wired signals, making wireless media less secure by default.
IV. Match the Following
Set A:
| Column A | Column B |
|---|
| 1. Twisted pair | (c) UTP / STP |
| 2. Coaxial cable | (d) Copper core + braid |
| 3. Fibre optic | (a) Light pulses |
| 4. RJ-45 | (e) 8-pin Ethernet connector |
| 5. BNC | (b) Coaxial connector |
Set B:
| Column A | Column B |
|---|
| 1. Radio wave | (d) Omnidirectional |
| 2. Microwave | (a) Line-of-sight |
| 3. Infrared | (e) Short-range, no penetration |
| 4. Satellite | (b) Long-distance relay |
| 5. Bluetooth | (c) Short-range radio (2.4 GHz) |
V. Short Answer Questions
1. Differentiate between UTP and STP cables.
Answer
| Feature | UTP | STP |
|---|
| Shielding | No metallic shield | Metallic foil/braid shield |
| Cost | Lower | Higher |
| EMI protection | Less | More |
| Flexibility | More flexible | Less flexible |
| Installation | Easier | Slightly harder |
| Use case | Office LANs | Industrial/noisy environments |
2. List any four advantages of fibre optic cable. 1. Very high bandwidth and data transfer speed 2. Immune to electromagnetic interference 3. Can transmit over long distances without repeaters 4. More secure — difficult to tap without detection 5. Lighter and thinner than copper cables
3. What are the disadvantages of wireless media?
Answer
- Security risk — signals can be intercepted by anyone within range
- Subject to interference from other devices and weather conditions
- Generally lower data transfer rates compared to wired media
- Limited range requiring repeaters or access points
- Reliability affected by physical obstacles
4. Name the types of coaxial cable and their maximum segment lengths.
Answer
- Thinnet (RG-58 / 10Base2): maximum segment length ~185 m
- Thicknet (RG-11 / 10Base5): maximum segment length ~500 m
5. What is the role of a connector in networking? A connector physically links a cable to a network device (NIC, switch, hub) and ensures proper signal transmission. Different cable types use specific connectors: RJ-45 for twisted pair, BNC for thin coaxial, SC/ST for fibre optic.
6. Write a short note on satellite communication. Satellite communication uses an orbiting satellite as a relay station to transmit data between two Earth stations. It covers a large geographical area (footprint), making it ideal for remote areas. Geostationary satellites orbit at 35,786 km. The main disadvantage is propagation delay (~270 ms round trip) and high deployment cost.
VI. Detailed Answer Questions
1. Compare guided and unguided transmission media with examples.
Answer
| Feature | Guided (Wired) | Unguided (Wireless) |
|---|
| Signal path | Through physical cable | Through free space |
| Examples | Twisted pair, coaxial, fibre optic | Radio, microwave, infrared, satellite |
| Interference | Less (especially fibre) | More susceptible |
| Security | Higher | Lower (signals travel openly) |
| Installation cost | Higher (cabling) | Lower (no cables) |
| Mobility | Limited | High |
| Bandwidth | Generally higher | Generally lower |
| Range | Limited by cable type | Can cover vast areas (satellite) |
Guided media provide a controlled path for signals, offering better security and bandwidth. Unguided media offer mobility and easy deployment but face interference and security challenges.
2. Explain the structure and working of fibre optic cable.
Answer
Structure: A fibre optic cable consists of:
- Core — the innermost thin strand of glass/plastic through which light travels
- Cladding — a layer of glass/plastic with a lower refractive index surrounding the core, reflecting light back inward (total internal reflection)
- Buffer coating — outer protective jacket made of plastic or Kevlar for mechanical strength
WorkingData is converted into light pulses using a laser (single-mode) or LED (multi-mode) at the transmitter end. The light travels through the core by total internal reflection — bouncing off the cladding boundary. At the receiver end, a photodetector converts the light pulses back into electrical signals.
Types:
- Single-mode fibre: Very thin core (8-10 microns), uses laser, long distance (up to 100 km), higher cost
- Multi-mode fibre: Wider core (50-62.5 microns), uses LED, shorter distance (up to 2 km), lower cost
3. Describe the types of wireless transmission media in detail.
Answer
| Type | Frequency | Range | Direction | Applications |
|---|
| Radio waves | 3 kHz–1 GHz | Long | Omnidirectional | AM/FM radio, Wi-Fi, cellular |
| Microwaves | 1–300 GHz | Medium-Long | Directional (line-of-sight) | Satellite links, point-to-point |
| Infrared | 300 GHz–400 THz | Short | Line-of-sight | TV remotes, IrDA, short-range data |
| Satellite | Various bands | Very long | Relay via satellite | TV broadcast, GPS, remote internet |
- Radio waves are omnidirectional, can penetrate walls, and are used for broadcasting and Wi-Fi (2.4/5 GHz).
- Microwaves are directional and require line of sight; used in terrestrial microwave towers and satellite uplinks/downlinks.
- Infrared is short-range, cannot penetrate walls, and is used for device-to-device communication at close range.
- Satellite communication uses a satellite relay to cover large areas but introduces propagation delay.
4. Compare coaxial cable and twisted pair cable.
Answer
| Feature | Coaxial Cable | Twisted Pair Cable |
|---|
| Structure | Central conductor + insulation + braid + jacket | Twisted pairs of insulated copper wires |
| Shielding | Metallic braid shield | UTP: none; STP: foil/braid |
| Bandwidth | Higher than UTP, lower than fibre | Lower than coaxial |
| EMI protection | Good (due to braid) | UTP: poor; STP: moderate |
| Connector | BNC, F-connector | RJ-45 |
| Cost | Moderate | Low (UTP) to moderate (STP) |
| Use case | Cable TV, broadband internet | Ethernet LANs, telephone lines |
| Maximum segment | 185 m (Thinnet), 500 m (Thicknet) | ~100 m (per segment) |
5. What are the advantages and disadvantages of wireless media compared to wired media?
Answer
Advantages of wireless media: 1. Mobility — users can move freely within the coverage area 2. No cabling cost — eliminates the expense of laying cables 3. Easy deployment — quick setup, useful for temporary networks 4. Covers difficult terrain — can reach areas where cabling is impractical (rural, hilly) 5. Scalability — adding devices requires no new cables
Disadvantages of wireless media: 1. Security risk — signals can be intercepted; needs encryption (WPA2, WPA3) 2. Interference — affected by weather, walls, and other electromagnetic sources 3. Lower bandwidth — speeds generally lower than wired (especially fibre) 4. Reliability — signal drops, dead zones, and congestion are common 5. Health concerns — prolonged exposure to radio frequency radiation is debated
Common Mistakes
1. Confusing fibre optic with copper cable — Fibre optic uses light, not electrical signals; it is immune to EMI. 2. Equating "free" wireless with "secure" — Wireless signals are broadcast and can be intercepted; always mention encryption. 3. Saying microwave can penetrate buildings — Microwaves require line of sight and are blocked by obstacles. 4. Mixing up RJ-45 and RJ-11 — RJ-45 (8 pins) is for Ethernet; RJ-11 (4 or 6 pins) is for telephone. 5. Confusing single-mode and multi-mode fibre — Single-mode has a smaller core, uses laser, and covers longer distances; multi-mode has a wider core, uses LED, and covers shorter distances. 6. Omitting the cladding in fibre optic structure — The cladding enables total internal reflection; without it, light escapes the core. 7. Forgetting propagation delay in satellite communication — Always mention the ~270 ms round-trip delay for geostationary satellites.
Exam Checklist
- [ ] Can list and describe three types of guided media (twisted pair, coaxial, fibre optic)
- [ ] Can explain UTP vs STP with differences
- [ ] Know the structure and working of fibre optic cable (core, cladding, total internal reflection)
- [ ] Can differentiate single-mode vs multi-mode fibre
- [ ] Know connector types: RJ-45, BNC, SC, ST and which cable each belongs to
- [ ] Can name and describe four types of unguided media (radio, microwave, infrared, satellite)
- [ ] Understand line-of-sight requirement for microwave and infrared
- [ ] Can compare wired vs wireless media (at least 4 points each)
- [ ] Know segment lengths: Thinnet (~185 m), Thicknet (~500 m), UTP Ethernet (~100 m)
- [ ] Can explain total internal reflection in fibre optics
