Communications Reviewer 1 Multiple Choice

SMS, or Short Message Service, is a means of sending short messages to and from mobile phones. It is often referred to as text messaging. This service allows users to send and receive brief messages, typically limited to 160 characters. SMS has become a popular form of communication due to its convenience and widespread availability on mobile devices. It is not to be confused with LMS (Long Message Service) or MMS (Multimedia Message Service), which offer different capabilities for sending longer messages or messages with multimedia content.

Plumbicon is the correct answer because it is a type of camera tube that is made from lead oxide (PbO). Lead oxide is used in the construction of Plumbicon tubes because it has high sensitivity to light and can generate a high-quality video signal. Plumbicon tubes were commonly used in professional video cameras and offered better performance compared to other camera tube technologies such as Saticon, Pasecon, and Trinicon.

Polytetrafluoroethylene, commonly known as Teflon, is a synthetic fluoropolymer of tetrafluoroethylene. It is well-known for its nonstick properties and is widely used as a coating for cookware and in various industrial applications. Teflon is highly resistant to heat, chemicals, and electrical conductivity, making it a versatile material. Micah, glass, and tissue are unrelated to polytetrafluoroethylene and do not refer to its alternate names or characteristics.

Divx is the correct answer because it is a popular video codec that uses Mpeg 4 video compression. It allows for high-quality video playback while maintaining a relatively small file size. Divx is widely used for compressing and distributing videos over the internet, making it a suitable choice for radio formats that incorporate video content. Divv, Divy, and Divz are not valid options as they do not correspond to any known video compression formats.

MPEG 4 is the correct answer because it is the current digital video specification that is widely used for video compression. MPEG 4 provides efficient compression algorithms, allowing for high-quality video playback and streaming over various platforms and devices. It offers advanced features such as object-based coding, interactivity, and scalability, making it suitable for a wide range of applications including video conferencing, streaming services, and multimedia content delivery.

The correct answer is Inertial Navigation System. Inertial navigation is a type of navigation system that relies on Newton's laws of motion. It uses accelerometers and gyroscopes to measure changes in velocity and direction, allowing for accurate tracking of an object's position and movement. This system is commonly used in aircraft, submarines, and spacecraft, where GPS signals may be unavailable or unreliable.

William Gibson is the correct answer because he is the science fiction author who coined the term "cyberspace" in his 1984 novel "Neuromancer." Gibson's novel popularized the concept of a virtual reality space accessed through computer networks, and his use of the term has since become widely adopted in discussions about the internet and digital technology.

Hydrazine is the correct answer because it is a highly reactive and toxic chemical compound that is commonly used as a propellant in rocket and jet engines. It is known for its high energy content and ability to generate large amounts of thrust, making it an ideal fuel for powering aircraft engines. Additionally, hydrazine has a low freezing point and is stable at high temperatures, further enhancing its suitability for use in jet engines.

Antonio Meucci is credited with the invention of the telephone. He was an Italian inventor and is known for developing a working prototype of the telephone in the 1840s. Although Alexander Graham Bell is often associated with the invention of the telephone, Meucci's contributions were acknowledged by the US Congress in 2002, recognizing him as the true inventor of the telephone.

A flat top sample refers to the sampling of an analog signal using a sample and hold circuit in such a way that the sampled signal maintains a constant amplitude throughout its entire duration. This means that the sampled signal does not experience any variations or fluctuations in its amplitude during the sampling process.

The correct answer is "horn with parabolic reflector which rotates 360 degree". This type of antenna is commonly used in radar systems because it provides a wide coverage area and allows for scanning the entire surrounding space. The rotation of the antenna helps in detecting and tracking objects from different directions, ensuring comprehensive radar coverage. The horn shape of the antenna helps in focusing and directing the radar signals, while the parabolic reflector enhances the antenna's gain and directivity.

The correct answer is WiMax. In 2002, a standard for Broadband Wireless Access (BWA) was introduced, which is commonly known as 802.16 in the IEEE standard. WiMax is a technology that is based on this standard and provides wireless broadband access over long distances. It allows for high-speed internet connections and is often used in areas where wired connections are not feasible or cost-effective. WiBro and Zigbee are other wireless communication technologies, but they are not directly related to the 802.16 standard. Therefore, the correct answer is WiMax.

Exposure to sound levels between 100 dB and 110 dB should not exceed 20 minutes. This is because prolonged exposure to high sound levels can cause damage to the ears and lead to hearing loss. The 20-minute limit helps to protect individuals from the potential harmful effects of loud noise.

A video signal that has no sync signal is referred to as a non-composite video signal. This means that the video signal does not include the synchronization information necessary for proper display. In a composite video signal, the sync signal is combined with the video signal to ensure correct timing and synchronization between the display device and the video source. Therefore, a video signal without a sync signal would be considered a non-composite video signal.

An ionosonde is an instrument used to measure the virtual height of the ionosphere. It works by transmitting a radio wave signal towards the ionosphere and then receiving the reflected signal. By analyzing the time it takes for the signal to travel and return, the ionosonde can determine the virtual height of the ionosphere at different frequencies. This information is crucial for studying and understanding the behavior of the ionosphere, which is important for various applications like radio communication and navigation systems.

An ionosonde is an instrument used to measure the relative height and layers in the ionosphere in terms of wave propagation. It is specifically designed to study the ionosphere and its characteristics, such as electron density, frequency, and amplitude of radio waves. By sending out radio waves and analyzing the reflected signals, an ionosonde can provide valuable information about the ionosphere's structure and behavior. The other options, Isocone, Ionicode, and Virtual Ion, are not instruments used for this purpose and are not related to measuring the ionosphere.

Ephemeris refers to a table or data that provides the pre-calculated positions of a satellite at any given time. It is a valuable resource for tracking and predicting the location of satellites. The term "Edomeris" is not a recognized term in this context, and therefore, it is not a correct answer. The correct answer is "Ephemeris."

Edwin Armstrong developed the superheterodyne receiver. The superheterodyne receiver is a type of radio receiver that uses frequency mixing to convert the incoming radio frequency signal to a fixed intermediate frequency. This intermediate frequency is easier to amplify and process, resulting in better signal quality and selectivity. Armstrong's invention revolutionized radio technology and became the standard for radio receivers, leading to significant advancements in communication systems.

The correct answer is Inertial Navigation System. This type of navigation system is currently used in aircraft, submarines, spacecraft, and guided missiles. It uses a combination of accelerometers and gyroscopes to measure the vehicle's acceleration and rotation, allowing it to calculate its position and orientation. This system is independent of external references such as GPS and is therefore highly reliable and accurate.

The correct answer is 20 PHON. PHON is a unit used to measure the loudness level of a sound. A watch ticking is a relatively quiet sound, so it would have a low loudness level. Therefore, 20 PHON is the most appropriate option as it represents a low level of loudness.

HDTV has 1125 horizontal scanning lines. This means that the screen is divided into 1125 horizontal rows, each containing pixels that make up the image. The more scanning lines a display has, the higher the resolution and clarity of the image. Therefore, 1125 is the correct answer for the number of horizontal scanning lines in HDTV.

The antenna height of a CB (Citizen Band) radio is 60 ft above the ground and 20 ft above the building.

When the total via net loss of a given trunk circuit in a telephone channel exceeds approximately 2.5 dB, an Echo Suppressor is inserted. An Echo Suppressor is a device used to reduce or eliminate the echo that occurs during a phone call. It helps to improve the quality of the audio by suppressing the echo caused by the transmission of the signal.

AC-3 Dolby is the correct answer because it is a sound file format commonly used in North America as a substitute for MP3. AC-4, AC-5, and AC-2 Dolby are not commonly used sound file formats and therefore not suitable substitutes for MP3.

802.15.4 is a standard for low-rate wireless personal area networks (WPANs). Zigbee is a communication protocol built on top of the 802.15.4 standard, specifically designed for low-power, low-data-rate, and short-range wireless communication. Therefore, Zigbee is the correct answer as it is a well-known and widely used technology that is based on the 802.15.4 standard. WiMax and WiBro are different wireless communication standards that operate in different frequency ranges and have different characteristics, so they are not equivalent to 802.15.4.

The correct answer is apogee kick motor. A satellite is put into its final geosynchronous orbit from its transfer orbit by firing the apogee kick motor. The apogee kick motor is responsible for providing the necessary thrust to increase the satellite's apogee (the point in its orbit farthest from the Earth) and adjust its orbit to achieve the desired geosynchronous orbit. This motor is typically used to circularize the satellite's orbit and ensure it stays in a fixed position relative to the Earth's surface.

Helical antennas are often used for satellite tracking at VHF because of the Faraday Effect. The Faraday Effect refers to the rotation of the plane of polarization of electromagnetic waves as they pass through a medium under the influence of a magnetic field. This effect is utilized in helical antennas to improve their performance in receiving and transmitting signals. The helical shape of the antenna allows for a larger surface area, resulting in better reception and transmission of VHF signals. Additionally, the Faraday Effect helps to reduce interference and improve the antenna's ability to track satellites accurately.

For SSB (Single Sideband) transmitters, the average power is typically 1/4 to 1/3 of the peak envelope power. This means that the power of the transmitted signal, on average, is about one-fourth to one-third of the maximum power that the transmitter is capable of producing. This is because SSB modulation techniques allow for the elimination of one of the sidebands and the carrier signal, resulting in a more efficient use of power compared to other modulation techniques. Additionally, the typical human speech signal has a dynamic range that is well-suited for this power range.

The other term for parity check is Vertical Redundancy Check. This method is used to detect errors in data transmission by adding an extra bit to each data unit. This extra bit is used to ensure that the total number of 1s in the data unit, including the extra bit, is either even or odd. If the count of 1s does not match the expected parity, an error is detected. Therefore, the term "Vertical Redundancy Check" is synonymous with parity check.

The term "initial payload" refers to the bigger satellite that is launched first from the rocket. This satellite is responsible for carrying and deploying the smaller satellite into space. Once the smaller satellite is launched, the bigger satellite's mission is complete, and it will continue to propel in space while the smaller satellite carries out its intended tasks.

Metal film resistors are commonly used to reduce flicker noise voltage in electronic circuits. Flicker noise, also known as 1/f noise, is a type of noise that increases at lower frequencies. Metal film resistors have a low noise level and are known for their stability and accuracy. They provide a consistent and reliable performance, making them suitable for applications where low noise is essential. Carbon film resistors, on the other hand, tend to have higher noise levels and are not as effective in reducing flicker noise voltage. Mono film and cinema film are not relevant to the reduction of flicker noise voltage.

When the angle of incidence is equal to the angle of refraction, it means that the light is entering the fiber optics at a specific angle and bending at the same angle as it passes through the interface between two mediums. This phenomenon is known as total internal reflection. In this case, the light continues to travel along the normal path, following the direction perpendicular to the interface.

LMDS operates at a frequency range of 27 - 31 GHz. This frequency range is commonly used for wireless broadband communication. LMDS is a wireless communication technology that provides high-speed data transmission over short distances. It is often used in urban areas where the deployment of wired infrastructure is difficult or expensive. The 27 - 31 GHz frequency range allows for high data transfer rates and low latency, making it suitable for applications that require fast and reliable internet connectivity.

Proxima Centauri is the nearest star to our solar system. It is a red dwarf star located about 4.24 light-years away from Earth in the Alpha Centauri star system. Proxima Centauri is closer to us than any other known star, making it the correct answer to the question. Neutron stars and white dwarfs are different types of stars that are not the closest to our solar system. Orion, on the other hand, is not a star but a constellation in the night sky.

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The successor of Bluetooth after Lisbon is Seattle. This implies that Seattle is the next technology or version that is expected to replace or succeed Bluetooth after Lisbon.

Carrier frequency refers to the frequency of the electromagnetic wave that is used to carry the information signal in a communication system. It is also known as the "rest frequency" because it represents the base frequency at which the carrier wave operates. The other options, such as "courier freq," "horse freq," and "navigational freq," do not accurately describe the concept of carrier frequency and are therefore incorrect.

Terrestrial microwave antennas typically have an input and output impedance of 50 ohms. This impedance value is commonly used in microwave communication systems, as it provides a balanced and efficient transfer of power between the antenna and the transmission line. It ensures minimal signal loss and maximizes the signal strength, making it the standard impedance for many microwave antenna designs.

The camera picks up the part of the visible spectrum that has the greatest output in the Yellow Green range. This means that the camera is most sensitive to capturing light in this specific range, resulting in a higher output or intensity of colors in the Yellow Green region.

Backhaul refers to a terrestrial communications channel that connects an earth station to a local switching network or population center. It is the transmission of data from a remote site back to a central site or data center. This term is commonly used in the telecommunications industry to describe the network infrastructure that carries data traffic between cell towers and the core network. It is an essential component in providing reliable and efficient communication services to end-users.

Microwave communication involves transmitting signals using microwave frequencies. These signals can travel long distances without the need for repeaters. However, as the distance increases, the signal strength weakens. A repeater is used to amplify and regenerate the signal, ensuring it reaches its destination without significant degradation. In this case, the correct answer is 40 km, indicating that after this distance, a repeater is typically required to maintain the signal quality in microwave communication.

Middle C is a specific musical note that is commonly used as a reference point in music. It is typically defined as having a frequency of 262 Hz. This means that the sound wave of middle C repeats 262 times in one second. The other options provided (363 Hz, 633 Hz, and 622 Hz) are not the correct frequencies for middle C.

An acoustician is a scientist who specializes in the study of acoustics, which is the branch of physics that deals with the properties of sound and how it interacts with its environment. Acousticians conduct research, design and analyze acoustic systems, and provide solutions for various applications such as noise control, audio engineering, and architectural acoustics. Therefore, the correct answer is Acoustician.

The frequency of the upper side/above middle C is 524 Hz. This means that when playing a note above middle C on a musical instrument, the sound wave produced will vibrate at a frequency of 524 times per second.

In a trapezoid modulation, the 100% modulation will result in a triangular waveform. This is because trapezoid modulation involves varying the amplitude of a carrier signal by a modulating signal. When the modulation is at 100%, the amplitude of the carrier signal is fully varied, resulting in a waveform that resembles a triangle with straight sides and a pointed peak.

The correct answer is 45 MHz. In a CMTS (Cable Modem Termination System), the forward channel is used to transmit data from the service provider to the end user, while the reverse channel is used for data transmission from the end user to the service provider. The frequency separation between these two channels is important to prevent interference and ensure efficient communication. In this case, the frequency separation is 45 MHz, meaning that there is a gap of 45 MHz between the frequencies used for the forward and reverse channels.

A GPS satellite completes its orbit in 12 hours. This is because the GPS satellite system is designed to have satellites in six different orbital planes, with each plane containing four satellites. The satellites are evenly spaced in their respective planes to ensure continuous coverage. By having satellites in multiple planes, the system can provide global coverage. Each satellite orbits the Earth twice a day, taking approximately 12 hours to complete one orbit. This allows for accurate positioning and navigation data to be transmitted to GPS receivers on the ground.

The typical value of the velocity factor of an open wire transmission line is 0.9. Velocity factor is a measure of how fast a signal travels through a transmission line compared to the speed of light in a vacuum. A value of 0.9 means that the signal travels at 90% of the speed of light in a vacuum.

A single button microphone is commonly known as a Carbon Button microphone. This type of microphone uses a carbon button as the main component to convert sound waves into electrical signals. The carbon button acts as a variable resistor, changing its resistance as it vibrates in response to sound waves. This variation in resistance is then converted into an electrical signal that can be amplified and transmitted.

"Cheapernet" is the colloquial name for the term "Thin Ethernet". This term refers to a type of Ethernet cabling that is less expensive and thinner than the standard Ethernet cabling. It was commonly used in the early days of networking when cost was a significant factor. The name "Cheapernet" reflects the cost-effectiveness of this type of cabling compared to other options.