The frequency range at which land coaxial cables are used is
Answer: A
Correct answer: 106 to 108 Hz
Land coaxial cable is used from about 1 MHz to 100 MHz. Below that the cable's advantage over twisted pair is slight; above it attenuation rises sharply and waveguide or fibre is preferred.
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What uses a physical star topology ?
Answer: C
Correct answer: 10 base T
10Base-T runs twisted pair from each station to a central hub, which is a physical star. 10Base5 and 10Base2 are coaxial buses.
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The monitor station in what standard ensures that one and only one token is circulating ?
Answer: B
Correct answer: 802.5
IEEE 802.5 is Token Ring, and one station on the ring is designated the active monitor, whose duties include removing orphaned frames and ensuring exactly one token circulates. 802.3 is Ethernet, which has no token.
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What can happen at a Token Ring station
Answer: D
Correct answer: All of these
Every station on a Token Ring acts as a repeater: it examines the destination address to see whether the frame is for it, regenerates the signal, and passes the frame on round the ring.
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In Token Ring, when a frame reaches its destination station, then
Answer: D
Correct answer: both (a) and (b)
The destination does not remove the frame; it copies the data and sets the address-recognised and frame-copied bits in the frame status field - four bits in all. The frame continues round to the sender, which removes it, and that is how the sender learns the frame was received.
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Which of the following is not a transceiver function?
Answer: C
Correct answer: Addition and subtraction of headers
A transceiver sits at the physical layer: it transmits and receives the signal, monitors the line voltage and detects collisions. Building and stripping headers is the data link layer's work.
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The station-to-hub distance in which of the following is 2000 meters ?
Answer: B
Correct answer: 100 Base-FX
100Base-FX uses optical fibre, which reaches 2000 m. The copper varieties - TX and T4 - are limited to 100 m.
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Ether LAN uses
Answer: C
Correct answer: manchester encoding
Ethernet uses Manchester encoding: each bit is sent as a transition in the middle of its interval, so the receiver recovers the clock from the data itself and no separate timing signal is needed. The price is twice the bandwidth.
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Which of the given below houses the switches in Token Ring ?
Answer: B
Correct answer: MAU
The Multistation Access Unit holds the relays that close the ring: a station's connection is switched in when it is powered and bypassed when it is not, so one dead station does not break the ring.
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Which of the following uses an 8B/6T encoding scheme?
Answer: C
Correct answer: 100 Base-T4
100Base-T4 uses 8B/6T coding - eight bits mapped to six ternary symbols - which is what allows 100 Mbps over four pairs of ordinary Category 3 cable.
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