Data Communications - Physical Layer

The statement is true. In an unguided transmission medium, such as wireless communication, the direction of propagation of a signal depends on the direction in which it was emitted. Additionally, any obstacles or interference encountered by the signal while propagating can also affect its direction.

Transmission media refers to the physical means through which data is transmitted, such as cables or wireless signals. These media should ideally be transparent to data, meaning they should not alter or modify the data being transmitted. Their sole purpose is to transport the bits of data accurately and efficiently between computers, networks, and other equipment. Therefore, the statement that transmission media should be transparent to data is true.

The statement is true. The transmission medium refers to the physical pathway through which signals are transmitted from a transmitter to a receiver in a communication system. It can be a wired medium like copper cables or fiber optics, or a wireless medium like radio waves or satellite signals. The choice of transmission medium depends on factors like distance, data rate, cost, and environmental conditions.

A geostationary satellite is a satellite that appears stationary with respect to a fixed point on the rotating Earth. This means that it orbits the Earth at the same rotational speed as the Earth itself, resulting in the satellite always remaining above the same point on the Earth's surface. This type of satellite is commonly used for telecommunications, weather monitoring, and broadcasting, as it allows for continuous coverage of a specific area on the Earth's surface.

A twisted pair is formed by twisting two insulated conductors around each other. This twisting helps to reduce electromagnetic interference and crosstalk between the two conductors. The close proximity of the twisted wires also helps to improve the overall signal quality and reduce signal loss. Twisted pairs are commonly used in telecommunications and computer networking applications.

The disadvantage of using optical fiber technology is that fiber optic transmitters and receivers are still relatively expensive compared to electrical interfaces. This means that the initial cost of implementing a fiber optic network can be higher than using traditional electrical interfaces.

The correct answer is "core". In a fiber optic cable, the core is the thin glass center through which the light travels. It is surrounded by the cladding, which has a lower refractive index to help keep the light within the core. The jacket and sheath are protective layers that surround the cladding and core, providing additional insulation and strength to the fiber optic cable.

Transmission lines can be used to propagate both DC and high-frequency AC signals. This is because transmission lines are designed to transmit electrical signals over long distances with minimal distortion. While DC signals do not have a frequency, transmission lines can still transmit them effectively. Additionally, transmission lines can also propagate high-frequency AC signals, which are commonly used in telecommunications and power transmission systems. Therefore, the statement that transmission lines can only be used to propagate DC or low-frequency AC signals is false.

When an electromagnetic wave encounters a boundary or obstacle, a portion of the wave is reflected back towards the source. These waves that travel from the load back toward the source are known as reflected waves. They carry information about the properties of the load or the boundary that caused the reflection.

The outer optical material surrounding the thin glass center of the fiber that reflects the light back into this thin glass is called cladding. Cladding is a layer with a lower refractive index than the core, which helps to confine the light within the core and prevent it from escaping. This arrangement allows for efficient transmission of light signals through the fiber optic cable.

The plastic coating that protects the fiber from damage and moisture is called a jacket. The jacket acts as a protective layer around the fiber, preventing any external elements from causing harm to the fiber optic cable. It provides insulation and keeps the fiber safe from physical damage and moisture, ensuring the efficient transmission of signals through the fiber.

The physical layer is the lowest layer of the OSI protocol hierarchy, responsible for the actual transmission of data over a communication network. It deals with the physical aspects of the communication, including the transmission medium. The transmission medium refers to the physical medium through which the data is transmitted, such as cables, fiber optics, or wireless signals. Therefore, the correct answer is transmission medium.

Wireless transmission refers to the transfer of information over a distance without the use of electrical conductors. This method utilizes electromagnetic waves to transmit signals through the air or space. Unlike computer, coaxial cable, and fiber optics, which all involve the use of physical conductors to transmit data, wireless transmission allows for the transfer of information without the need for direct physical connections.

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The trunks of the telephone system refer to the pathways or lines that connect the switching offices. These trunks are often made of digital fiber optics, which provide high-speed and reliable communication between the different offices. The trunks play a crucial role in transmitting voice and data signals over long distances, ensuring efficient and effective communication within the telephone system.

Low-Earth Orbit Satellites are the correct answer because they orbit at a relatively close distance to Earth compared to geostationary and medium-Earth orbit satellites. These satellites are typically located between 180 to 2,000 kilometers above the Earth's surface. They have a faster orbital speed, which allows them to complete orbits in a shorter period of time. This proximity to Earth enables low-Earth orbit satellites to provide faster data transmission, lower latency, and better coverage for applications such as communication, weather monitoring, and Earth observation.

The answer is true because optical fibers are designed to contain the electromagnetic fields within the fiber, preventing them from radiating outwards. This is one of the advantages of using fiber optic cables as they do not produce electromagnetic interference or have any impact on nearby electronic devices.

The inner part of a coaxial cable is commonly known as the copper core or simply the core. This refers to the central conductor of the cable, which is typically made of copper. The core is surrounded by an insulating layer and then a metallic shield, followed by an outer protective layer. The copper core is responsible for carrying the electrical signals through the cable, while the other layers provide insulation and protection against interference.

Electromagnetic waves are produced when an electric charge undergoes acceleration. As the charge accelerates, it creates a changing electric field, which in turn generates a changing magnetic field. These changing electric and magnetic fields then propagate through space as electromagnetic waves. Therefore, an electric charge is the source of electromagnetic waves.

Wave velocity is the correct answer because it refers to the speed at which waves travel. The velocity of a wave can vary depending on the type of wave and the characteristics of the medium through which it is propagating. This means that different waves, such as sound waves or light waves, can travel at different speeds. The velocity of a wave is typically measured in meters per second (m/s) and is calculated by dividing the distance traveled by the wave by the time it takes to travel that distance.

An example of a transverse wave is the surface wave of water. This statement is false. The surface wave of water is actually an example of a type of wave called a "capillary wave", which is a combination of both longitudinal and transverse wave motion. Transverse waves are characterized by the particles of the medium oscillating perpendicular to the direction of wave propagation, while longitudinal waves have particles oscillating parallel to the direction of wave propagation.

Transverse waves are characterized by their displacement being perpendicular to the direction of propagation. This means that as the wave moves forward, the particles of the medium through which the wave is traveling move up and down or side to side, rather than back and forth in the same direction as the wave. This is in contrast to longitudinal waves, where the displacement is parallel to the direction of propagation. Sound waves and surface waves of water can both be examples of transverse waves.

Category 5 UTP is actually intended to be used in high-speed local area networks with data rates of up to 100 Mbps. Therefore, the statement that it is intended for use in low-speed networks with data rates of 16 Mbps and below is incorrect.

A transverse wave is an oscillatory motion. Transverse waves are characterized by particles in the medium moving perpendicular to the direction of the wave propagation. This motion is back and forth or up and down, creating a pattern of oscillations. Therefore, the correct answer is oscillatory.

The Data Link Layer is not a fundamental layer upon which all higher level functions in a network are based. It is actually the second layer in the OSI model and is responsible for the reliable transmission of data between nodes on a network. The Network Layer is the fundamental layer upon which all higher level functions are based, as it is responsible for routing and forwarding data packets across different networks. Therefore, the statement is false.

The given statement is false because fiber optic technology does not make use of electricity to carry digital signals. Instead, it uses light signals to transmit data through optical cables. This technology relies on the principle of total internal reflection, where light is constantly reflected within the fiber optic cable, ensuring minimal signal loss and high data transmission speeds.

A medium-Earth orbit satellite is the most suitable option for facilitating high-speed telephone signals. Geostationary satellites are placed in a fixed position above the equator, which limits their coverage to specific regions. Low-Earth orbit satellites, on the other hand, are closer to the Earth's surface and are primarily used for applications such as remote sensing and global positioning systems. Therefore, a medium-Earth orbit satellite, which orbits between the geostationary and low-Earth orbits, provides a balance between coverage and signal quality, making it ideal for high-speed telephone signals.

The correct answer is sheath. The sheath is the outer covering of the fiber cables that protects the bundles of 2 or more fiber cables. It provides additional protection to the cables and helps prevent damage from external factors such as moisture, dust, and physical stress. The sheath is an essential component of fiber cables and plays a crucial role in maintaining the integrity and longevity of the cables.

Category 3 UTP is not intended for use in high-speed local area networks with a data rate of 100Mbps. Category 3 UTP is designed for use in networks with a maximum data rate of 10Mbps. For higher speeds, such as 100Mbps, Category 5 or higher cables are required.

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In the very low frequency bands, radio waves do not follow the atmospheric layers of the earth. They are able to penetrate the earth's surface and travel long distances, even beyond the line of sight. Therefore, the statement that radio waves in the very low frequency bands follow the atmospheric layers of the earth is false.

Switching offices in the telephone system are places where calls are moved from one trunk to another. These offices act as intermediaries, routing calls between different trunks to ensure that the call reaches its intended destination. They play a crucial role in connecting different parts of the telephone network and facilitating the efficient transfer of calls.

TRUE. Signals propagating down an unguided transmission medium, such as radio waves or Wi-Fi signals, can be received by anyone with a device capable of receiving them. Unlike guided transmission mediums, which use physical cables and have limited accessibility, unguided transmission mediums allow signals to travel freely through the air or space, making them accessible to anyone within range. This is why unguided transmission mediums are commonly used for broadcasting and wireless communication.

The spatial relationship between the electric and magnetic field in an electromagnetic wave where they are perpendicular to each other at all points is called "space quadrature". This means that the electric field vector is perpendicular to the magnetic field vector, forming a right angle. This relationship is a fundamental characteristic of electromagnetic waves and is essential for their propagation through space.

Longitudinal waves are characterized by the displacement of particles in the same direction as the wave propagation. In other words, the particles move back and forth parallel to the direction of the wave. This is different from transverse waves, where the particles move perpendicular to the direction of the wave. Electromagnetic waves, such as light, are also transverse waves. Sound waves, on the other hand, are longitudinal waves because they cause particles in a medium to vibrate back and forth in the same direction as the wave travels.

This cable consists of two copper wires that are individually covered with polyvinyl chloride insulation. The term "unshielded" means that there is no additional shielding layer around the wires. The term "twisted-pair" refers to the fact that the two wires are twisted together, which helps to reduce electromagnetic interference. Therefore, the correct answer is unshielded twisted-pair.

The distance of one cycle occurring in space is referred to as the wavelength. It represents the distance between two consecutive points in a wave that are in the same phase. The wavelength is typically measured from crest to crest or trough to trough. It is an important parameter in understanding the characteristics and behavior of waves, such as light and sound.

The term "visible" refers to the band of frequencies that the human eye is able to detect and respond to. This includes the range of colors that are perceivable by humans, typically ranging from red to violet. The human eye is not sensitive to frequencies outside of this visible spectrum, such as infrared or ultraviolet. Therefore, the correct answer is "visible" because it accurately describes the specific range of frequencies that the human eye can see.

Twin-lead is the correct answer because it consists of two metallic conductors separated by spacers and has a continuous solid dielectric that ensures uniform spacing along the entire cable. This description matches the characteristics of twin-lead cables, making it the most suitable option.

Electromagnetic waves that travel along a transmission line from the source to the load are referred to as incident waves. Incident waves are the waves that are initially generated by the source and propagate towards the load without any reflection or distortion. They carry the information or energy from the source to the load without being affected by any reflections or interference.

The correct answer is open-wire. Open-wire refers to a type of transmission line that consists of two or more metallic conductors separated by a nonconductive insulating material. This design allows for the transmission of electrical signals while minimizing interference and signal loss. Open-wire transmission lines were commonly used in early telecommunication systems before the advent of coaxial cables and other modern transmission technologies.

Infrared refers to the band of frequencies that is too high to be seen by the human eye. Infrared radiation has longer wavelengths than visible light, making it invisible to us. However, it can be detected and utilized for various purposes, such as in thermal imaging, remote controls, and communication systems. Infrared radiation is often associated with heat, as objects emit infrared radiation based on their temperature.

The physical layer of the OSI architecture is responsible for activating, maintaining, and deactivating network connections. This layer deals with the physical transmission of data over the network, including the electrical, mechanical, and functional aspects of the network interface. It ensures that the data is transmitted reliably between devices and handles tasks such as encoding, decoding, and transmitting signals. Therefore, the physical layer is the correct answer for this question.

The band of frequencies that are too low to be seen by the human eye refers to the range of electromagnetic waves known as infrared. Infrared waves have longer wavelengths than visible light, making them invisible to the naked eye. However, they can be detected and utilized by certain devices, such as infrared cameras and sensors. Infrared radiation is commonly used in various applications, including night vision technology, remote controls, and thermal imaging.

The type of coaxial cable which uses a dielectric material to separate conductors is called "insulated coaxial cable".

The type of coaxial cable which uses a solid dielectric material to separate conductors is called solid dielectric coaxial cable.

Guided transmission media refers to a category of transmission media that uses some form of conductor to provide a pathway for electromagnetic signals. This means that the signals are contained within the conductor, allowing for a more controlled and predictable transmission. Examples of guided transmission media include twisted-pair cables, coaxial cables, and optical fibers. These media provide a physical pathway for the signals to travel, ensuring better signal quality and less susceptibility to interference compared to unguided media.

The correct answer is "metallic cable." A metallic cable is a type of transmission line that is made of a metallic conductor. It is used to transfer electrical energy from one point to another by allowing electrical current to flow through it. This type of cable is commonly used in various applications to transmit electricity efficiently and safely.