Which of the following types of coaxial cable is used for cable TV and cable modems?
Answer(s): A
RG-59 type of coaxial cable is used for cable TV and cable modems. Answer option C is incorrect. RG-8 coaxial cable is primarily used as a backbone in an Ethernet LAN environment and often connects one wiring closet to another. It is also known as 10Base5 or ThickNet.Answer option D is incorrect. RG-62 coaxial cable is used for ARCNET and automotive radio antennas. Answer option B is incorrect. RG-58 coaxial cable is used for Ethernet networks. It uses baseband signaling and 50-Ohm terminator. It is also known as 10Base2 or ThinNet.
Which of the following IEEE standards is used for white spaces in the TV frequency spectrum?
Answer(s): C
The IEEE 802.22 standard describes the Wireless Regional Area Network (WRAN). It is used for white spaces in the TV frequency spectrum. It is designed to operate in the TV broadcast band while assuring that no harmful interference is caused to the incumbent operation. The IEEE 802.22.1 standard is used for enhanced interference protection of licensed devices. Answer option A is incorrect. IEEE 802.19 is an IEEE standard related to the Wireless Coexistence Working Group (WG). It develops standards for coexistence between wireless standards of unlicensed devices. This standard also reviews the coexistence assurance (CA) documents produced by the working groups involved in developing new wireless standards for unlicensed devices. Answer option D is incorrect. IEEE 802.20 is an IEEE standard to enable worldwide deployment of multi-vendor interoperable mobile broadband wireless access networks. It is also known as Mobile Broadband Wireless Access (MBWA). This standard is specified according to a layered architecture, which is consistent with other IEEE 802 specifications. Answer option B is incorrect. IEEE 802.21 is an IEEE standard that enables handover and interoperability between heterogeneous network types including 802 and non-802 networks both. It is primarily meant for heterogeneous (vertical) handovers but can be used for homogeneous (horizontal) handovers as well.
Which of the following statements best describes a certification authority?
A certificate authority or certification authority (CA) is an entity that issues digital certificates for use by other parties. It is an example of a trusted third party. A CA issues digital certificates that contain a public key and the identity of the owner. The matching private key is not similarly made available publicly, but kept secret by the end user who generated the key pair. The certificate is also an attestation by the CA that the public key contained in the certificate belongs to the person, organization, server or other entity noted in the certificate. A CA's obligation in such schemes is to verify an applicant's credentials, so that users and relying parties can trust the information in the CA's certificates. A variety of standards and tests are used by CAs to do so. If the user trusts the CA and can verify the CA's signature, then he can also verify that a certain public key does indeed belong to whoever is identified in the certificate. Answer options B and A are incorrect. A certification authority (CA) is not a type of encryption. Answer option D is incorrect. A certification authority (CA) does not authenticate digital documents by using computer cryptography. In order to authenticate digital documents by using computer cryptography, a digital signature should be used.
Which of the following characteristics of cables signifies the amount of digital data that the cable carries?
Answer(s): D
Bandwidth (or digital bandwidth) is a measurement of how much data can be sent in a period of time. It is a data rate measured in bits. The standard unit of digital bandwidth is bits per second (bps). In radio communication, bandwidth (analogue bandwidth) is the range of frequencies occupied by the radio signals. The standard unit of analogue bandwidth is Hertz (Hz). Answer option B is incorrect. In physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, X-rays are attenuated by lead, and light and sound are attenuated while passing through seawater. In electrical engineering and telecommunications, attenuation affects the propagation of waves and signals in electrical circuits, in optical fibers, as well as in air (radio waves). Answer option A is incorrect. Crosstalk is a disturbance caused by the electric or magnetic fields of one telecommunication signal affecting a signal in an adjacent circuit. Within network circuits it can occur due to electromagnetic interference (EMI). It can occur in microcircuits within computers and audio equipments as well. Answer option C is incorrect. Each type of cable is susceptible to some interference. This interference may be internal or external noise. These noises depend on the environment where the cable is to be laid. External noise may consist of Electromagnetic Interference (EMI) or Radio Frequency Interference (RFI). EMI (electromagnetic interference) is the disruption of operation of an electronic device when it is in the vicinity of an electromagnetic field (EM field) in the radio frequency (RF) spectrum that is caused by another electronic device. Shielded cables are less susceptible to interference than unshielded cables.
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Keway Commented on January 09, 2025 It was excellent Anonymous
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