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BSNL JTO practice questions

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Question 1Telecom / Network Engineering (general technical section)

In a 2 Mbps PCM system using 8-bit samples, what sampling rate is required to satisfy the Nyquist criterion for a signal band-limited to 4 kHz?

  1. 8000 samples per second Correct answer.
  2. 16000 samples per second
  3. 4000 samples per second
  4. 2000 samples per second

Explanation

The Nyquist criterion requires a sampling rate of at least twice the highest signal frequency, so for a 4 kHz band limit the minimum is 8000 samples per second. With 8-bit encoding this gives 64 kbps per voice channel, and 30 such channels plus overhead fit a 2 Mbps E1 frame.

Question 2Telecom / Network Engineering (general technical section)

A fibre optic link uses a step-index multimode fibre. Which phenomenon primarily limits its bandwidth over long distances?

  1. Fresnel reflection at the connector
  2. Polarisation-dependent loss
  3. Stimulated Brillouin scattering
  4. Modal dispersion Correct answer.

Explanation

In step-index multimode fibre, different modes travel different path lengths and arrive at different times, causing modal dispersion that broadens the pulse and limits bit rate. Single-mode fibre avoids this because only one propagation mode exists.

Question 3Telecom / Network Engineering (general technical section)

Which OSI layer is responsible for logical addressing and path selection between networks?

  1. Transport layer
  2. Network layer Correct answer.
  3. Data link layer
  4. Session layer

Explanation

The network layer handles logical addressing such as IP addresses and routing decisions that select the path between networks. The data link layer handles physical addressing on a single link, while the transport layer provides end-to-end delivery.

Question 4Telecom / Network Engineering (general technical section)

In a telephone network, what does the term 'erlang' measure?

  1. Bit error rate on a trunk
  2. Battery voltage at the subscriber set
  3. Signal attenuation per kilometre
  4. Telephone traffic intensity Correct answer.

Explanation

One erlang represents one circuit occupied continuously for one hour, so erlangs express traffic intensity offered to or carried by a trunk group. Traffic engineering uses the erlang formula and tables to size trunk groups for a target grade of service.

Question 5Telecom / Network Engineering (general technical section)

What is the primary function of the HLR in a GSM network?

  1. Switching voice calls between mobile and PSTN
  2. Measuring call duration for billing at the exchange
  3. Storing permanent subscriber data and subscription profile Correct answer.
  4. Providing air-interface encryption keys per call

Explanation

The Home Location Register is the central database holding permanent subscriber information such as the IMSI, subscription services, and current VLR address. The VLR holds temporary visitor data, while the MSC performs switching.

Question 6Telecom / Network Engineering (general technical section)

Which modulation scheme is used for the downlink in LTE and carries data on many closely spaced orthogonal subcarriers?

  1. QAM with single carrier
  2. SC-FDMA
  3. GMSK
  4. OFDMA Correct answer.

Explanation

LTE downlink uses OFDMA, which distributes data across many orthogonal subcarriers and allows flexible scheduling in frequency. The uplink instead uses SC-FDMA to keep the peak-to-average power ratio low for the handset power amplifier.

Question 7Telecom / Network Engineering (general technical section)

What is the purpose of the cyclic prefix in an OFDM symbol?

  1. To increase the peak-to-average power ratio of the transmitted signal
  2. To synchronise the base station clocks across the network
  3. To provide channel coding gain against random bit errors
  4. To absorb multipath delay spread and prevent inter-symbol interference Correct answer.

Explanation

The cyclic prefix copies the tail of the OFDM symbol to its start, so delayed multipath replicas fall within the guard interval and orthogonality between subcarriers is preserved. It removes inter-symbol interference at the cost of a small spectral efficiency loss.

Question 8Telecom / Network Engineering (general technical section)

A 64 kbps channel is used with a signal-to-noise ratio of 15 (linear). Using the Shannon capacity formula, roughly what maximum data rate is achievable?

  1. About 16 kbps
  2. About 256 kbps Correct answer.
  3. About 960 kbps
  4. About 64 kbps

Explanation

Shannon capacity is C = B log2(1 + S/N). With B = 64 kHz and S/N = 15, log2(16) = 4, giving C = 256 kbps. This is the theoretical upper bound, so practical systems using the channel will operate below it.

Question 9Telecom / Network Engineering (general technical section)

In TCP, which mechanism prevents a fast sender from overwhelming a slow receiver?

  1. Congestion control using slow start
  2. Flow control using the advertised receive window Correct answer.
  3. Selective acknowledgement of lost segments
  4. Checksum validation of the header

Explanation

TCP flow control uses the receive window advertised by the receiver to limit how much unacknowledged data the sender may have in flight. Congestion control, by contrast, protects the network rather than the receiver.

Question 10Telecom / Network Engineering (general technical section)

Which address range is reserved for private use in IPv4 and is commonly used inside enterprise LANs?

  1. 10.0.0.0/8 Correct answer.
  2. 224.0.0.0/4
  3. 169.254.0.0/16 is globally routable
  4. 172.16.0.0/12 is public

Explanation

RFC 1918 defines 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 as private address blocks that are not routed on the public internet. Enterprises use them with NAT to connect internal hosts to the internet.

Question 11Telecom / Network Engineering (general technical section)

A subnet mask of 255.255.255.224 is applied to a network. How many usable host addresses does each subnet provide?

  1. 32
  2. 14
  3. 30 Correct answer.
  4. 62

Explanation

The mask 255.255.255.224 leaves 5 host bits (/27), giving 32 addresses per subnet. Subtracting the network and broadcast addresses leaves 30 usable host addresses.

Question 12Telecom / Network Engineering (general technical section)

What does the TTL field in an IPv4 header primarily prevent?

  1. Unauthorised access to internal hosts
  2. Packets circulating indefinitely due to routing loops Correct answer.
  3. Fragmentation of oversized datagrams
  4. Duplicate IP address assignment on a LAN

Explanation

Each router decrements the TTL by one and discards the packet when it reaches zero, which bounds the lifetime of a packet caught in a routing loop. Traceroute exploits this behaviour by deliberately sending packets with small TTL values.

Question 13Telecom / Network Engineering (general technical section)

In a GSM network, what is the role of the AUC in relation to the SIM?

  1. It performs handover between base station controllers
  2. It stores the visitor location of roaming subscribers
  3. It generates authentication triplets used to verify the subscriber Correct answer.
  4. It allocates radio channels to the mobile station

Explanation

The Authentication Centre holds the subscriber's secret key and produces the random challenge, signed response and ciphering key triplets that the MSC/VLR uses to authenticate the SIM. It works together with the HLR but is a separate network element.

Question 14Telecom / Network Engineering (general technical section)

Which statement correctly describes the difference between a circuit-switched and a packet-switched network?

  1. Circuit switching reserves a dedicated path for the call duration, while packet switching shares links statistically Correct answer.
  2. Circuit switching requires IP addressing, while packet switching uses E.164 numbers
  3. Circuit switching always carries voice, while packet switching always carries video
  4. Packet switching guarantees a fixed bandwidth per call, while circuit switching does not

Explanation

Circuit switching establishes and reserves a dedicated end-to-end path for the duration of the call, so capacity is wasted during silence. Packet switching statistically multiplexes packets from many users over shared links, improving efficiency at the cost of variable delay.

Question 15Telecom / Network Engineering (general technical section)

What is the main advantage of using a digital trunk with PCM and TDM over analogue frequency-division multiplexing in the access network?

  1. Lower requirement for synchronisation between exchanges
  2. Reduced need for channel coding in the transmission path
  3. Immunity to noise accumulation and easier regeneration of the signal Correct answer.
  4. Elimination of the need for any multiplexing equipment

Explanation

Digital regeneration restores the pulse shape and retimes the signal, so noise does not accumulate over long chains of repeaters as it does in analogue FDM. Digital trunks also simplify multiplexing and allow direct connection to digital switching.

Question 16Telecom / Network Engineering (general technical section)

In a cellular system, what is the purpose of frequency reuse with a cluster size N?

  1. To increase capacity by reusing the same channels in cells separated by a sufficient reuse distance Correct answer.
  2. To allow all cells to use the same frequency simultaneously without planning
  3. To synchronise the frame timing of all base stations
  4. To eliminate co-channel interference entirely across the network

Explanation

Frequency reuse divides the available spectrum into N channel groups and assigns them to cells so that the same frequencies are reused at a distance where co-channel interference is acceptable. Smaller N raises capacity but increases interference, so the reuse factor is a design trade-off.

Question 17Telecom / Network Engineering (general technical section)

Which multiple access technique assigns each user a unique spreading code and allows all users to transmit simultaneously in the same frequency band?

  1. FDMA
  2. CDMA Correct answer.
  3. TDMA
  4. OFDMA

Explanation

In CDMA, each user is given a distinct orthogonal or quasi-orthogonal spreading code, and all users share the same wideband channel at the same time. The receiver correlates with the desired code to separate that user's signal from the others.

Question 18Telecom / Network Engineering (general technical section)

In a PCM system, what is the effect of companding on the quantisation noise of weak signals?

  1. It reduces the required sampling rate for the same bandwidth
  2. It increases the number of bits per sample to 12 always
  3. It removes the need for a reconstruction filter at the receiver
  4. It improves the signal-to-quantisation-noise ratio for low-amplitude signals by using non-uniform steps Correct answer.

Explanation

Companding applies a logarithmic compression law, such as A-law or mu-law, so that small signal amplitudes are quantised with finer steps and large amplitudes with coarser steps. This improves the SNR for weak talkers while keeping the overall bit rate fixed.

Question 19Telecom / Network Engineering (general technical section)

A link has a bit rate of 1 Mbps and a one-way propagation delay of 10 ms. For a stop-and-wait protocol with negligible processing time, what is the approximate link utilisation for 1000-bit frames?

  1. About 96 percent
  2. About 0.5 percent
  3. About 4.8 percent Correct answer.
  4. About 50 percent

Explanation

Transmission time is 1000 bits / 1 Mbps = 1 ms. The round trip is 20 ms, so the sender waits about 21 ms per frame and utilisation is 1/21, approximately 4.8 percent. Sliding-window protocols improve this by keeping multiple frames in flight.

Question 20Telecom / Network Engineering (general technical section)

A 155.52 Mbps STM-1 frame carries a section overhead. What is the approximate payload capacity available to the higher-order path?

  1. 150.336 Mbps Correct answer.
  2. 155.52 Mbps
  3. 34.368 Mbps
  4. 2.048 Mbps

Explanation

STM-1 has a line rate of 155.52 Mbps, of which 9 bytes of each 270-byte row form the section overhead. Removing the section overhead leaves about 150.336 Mbps of payload capacity available for the administrative unit and path overheads.

Question 21Telecom / Network Engineering (general technical section)

In a GSM network, a mobile station moves from one location area to another. Which network element is updated first and why?

  1. The EIR is updated to allow the handset to attach to the new area
  2. The HLR is updated with the new cell identity, and the VLR remains unchanged
  3. The AUC is updated with new authentication triplets for the new area
  4. The VLR is updated with the new location area, and the HLR is informed of the serving VLR Correct answer.

Explanation

When a mobile enters a new location area it performs a location update to the VLR serving that area, which creates a visitor record and then informs the HLR of the new serving VLR. The HLR stores only the VLR address, not cell-level detail.

Question 22Telecom / Network Engineering (general technical section)

A router receives a packet destined for 192.168.10.130/26. To which subnet does the destination belong?

  1. 192.168.10.0/26
  2. 192.168.10.192/26
  3. 192.168.10.128/26 Correct answer.
  4. 192.168.10.64/26

Explanation

A /26 mask gives blocks of 64 addresses. The blocks are .0, .64, .128 and .192, so 192.168.10.130 falls in 192.168.10.128/26, which spans .128 to .191.

Question 23Telecom / Network Engineering (general technical section)

Why does a single-mode fibre have far lower dispersion than a multimode fibre at 1310 nm?

  1. Only the fundamental mode propagates, so intermodal dispersion is absent Correct answer.
  2. Its cladding is made of plastic that absorbs higher-order modes
  3. It carries a lower optical power that reduces chromatic effects
  4. Its core has a higher numerical aperture that traps all modes

Explanation

A single-mode fibre has a core diameter small enough that only the fundamental mode is guided, so intermodal dispersion cannot occur. The remaining limit is chromatic dispersion, which is small near the zero-dispersion wavelength around 1310 nm.

Question 24Telecom / Network Engineering (general technical section)

Which statement about the SS7 signalling network is correct?

  1. Signalling is carried on a separate packet network, so voice circuits are set up only after signalling completes Correct answer.
  2. Signalling uses the same time slot as the voice channel it controls
  3. Signalling messages are broadcast to all exchanges in the network simultaneously
  4. Signalling is carried in-band within each voice channel using DTMF tones

Explanation

SS7 uses a dedicated out-of-band packet-switched signalling network of signalling points and signalling transfer points. This allows fast call setup and advanced services, and the voice circuit is seized only after the signalling exchange completes.

Question 25Telecom / Network Engineering (general technical section)

What is the function of the GGSN in a GPRS core network?

  1. It allocates radio resources to the mobile station on the air interface
  2. It stores the permanent subscription data of the subscriber
  3. It provides the gateway between the GPRS network and external packet data networks Correct answer.
  4. It performs authentication of the mobile station with the AUC

Explanation

The GGSN acts as the interface between the GPRS backbone and external packet networks such as the internet, handling address allocation and tunnelling to the SGSN. The SGSN manages mobility and session management towards the mobile.

Question 26Telecom / Network Engineering (general technical section)

In a PCM system using 8-bit encoding, how many distinct quantisation levels can be represented?

  1. 256 Correct answer.
  2. 128
  3. 512
  4. 64

Explanation

An n-bit PCM code word can represent 2^n distinct levels, so 8 bits give 2^8 = 256 levels. This sets the quantisation step size relative to the full-scale input range.

Question 27Telecom / Network Engineering (general technical section)

Which ITU-T recommendation defines the PCM hierarchy used in Indian and European digital trunk networks, with 32 time slots per frame at 2048 kbps?

  1. G.732 Correct answer.
  2. G.703
  3. G.711
  4. G.823

Explanation

G.732 specifies the characteristics of primary PCM multiplex equipment operating at 2048 kbps with 32 time slots, the E1 hierarchy used in India. G.711 instead defines the companding law, while G.703 defines the physical interface.

Question 28Telecom / Network Engineering (general technical section)

In an SDH network, which byte in the section overhead carries the bit interleaved parity used for error monitoring over each regenerator section?

  1. E1
  2. D1
  3. A1
  4. B1 Correct answer.

Explanation

The B1 byte carries a bit interleaved parity (BIP-8) computed over the previous STM-N frame after scrambling, enabling in-service error monitoring of the regenerator section. B2 performs the equivalent function for the multiplex section.

Question 29Telecom / Network Engineering (general technical section)

A 1000-byte IP packet is fragmented for transmission over a link whose maximum transmission unit is 500 bytes. If the IP header is 20 bytes, how many fragments are produced?

  1. 5
  2. 2
  3. 3 Correct answer.
  4. 4

Explanation

Each fragment carries at most 480 bytes of data (500 minus the 20-byte header), and the data length must be a multiple of 8. The 1000 data bytes split as 480 + 480 + 40, giving three fragments.

Question 30Telecom / Network Engineering (general technical section)

Which protocol uses a three-way handshake with SYN, SYN-ACK and ACK before any application data is exchanged?

  1. ARP
  2. TCP Correct answer.
  3. ICMP
  4. UDP

Explanation

TCP establishes a connection with a synchronise, synchronise-acknowledge and acknowledge exchange, allowing both sides to agree initial sequence numbers. This connection-oriented setup underlies reliable, ordered delivery.

Question 31Telecom / Network Engineering (general technical section)

In OSPF, which packet type is used by a router to confirm that a neighbouring router is still alive on a point-to-point link?

  1. Database Description
  2. Link State Update
  3. Hello Correct answer.
  4. Link State Acknowledgement

Explanation

Hello packets are sent periodically on each interface to discover neighbours and to keep the adjacency alive; failure to receive them within the dead interval tears the adjacency down. The other packet types serve database synchronisation and flooding.

Question 32Telecom / Network Engineering (general technical section)

Which field in the IPv4 header is recomputed at every router that forwards the packet because it covers the header only?

  1. Protocol
  2. Header Checksum Correct answer.
  3. Total Length
  4. Identification

Explanation

The header checksum protects only the header, and because the TTL is decremented at each hop the checksum must be recalculated by every forwarding router. Payload integrity is left to upper layers.

Question 33Telecom / Network Engineering (general technical section)

Which IPv6 mechanism lets a host configure a globally routable address from a router-advertised prefix without a DHCPv6 server?

  1. Path MTU discovery
  2. Duplicate address detection
  3. Neighbour solicitation
  4. Stateless address autoconfiguration Correct answer.

Explanation

Stateless address autoconfiguration combines a router-advertised prefix with an interface identifier generated by the host, so no address-assigning server is needed. Duplicate address detection is a related but separate step that verifies uniqueness.

Question 34Telecom / Network Engineering (general technical section)

A link uses 16-QAM at a symbol rate of 2400 baud. What is the approximate gross bit rate?

  1. 2400 bps
  2. 9600 bps Correct answer.
  3. 7200 bps
  4. 4800 bps

Explanation

16-QAM carries log2(16) = 4 bits per symbol, so 2400 symbols per second give 2400 x 4 = 9600 bps. The bit rate scales with the number of bits mapped onto each symbol.

Question 35Telecom / Network Engineering (general technical section)

In a QPSK constellation, what is the phase separation between adjacent symbols?

  1. 45 degrees
  2. 180 degrees
  3. 90 degrees Correct answer.
  4. 270 degrees

Explanation

QPSK maps two bits per symbol onto four points spaced evenly around the circle, so adjacent symbols differ by 360/4 = 90 degrees. This spacing gives good noise immunity for the same average power.

Question 36Telecom / Network Engineering (general technical section)

Which technique spreads a signal by multiplying it with a fast pseudo-random code so that the received power spectral density falls below the noise floor?

  1. Frequency-division multiplexing
  2. Direct-sequence spread spectrum Correct answer.
  3. Amplitude shift keying
  4. Delta modulation

Explanation

Direct-sequence spread spectrum multiplies the data by a high-rate pseudo-random chip sequence, widening the bandwidth and lowering the power density so the signal can be recovered by correlation. This also provides processing gain against interference.

Question 37Telecom / Network Engineering (general technical section)

In a GSM network, which interface carries signalling between the mobile switching centre and the base station controller?

  1. Um interface
  2. Abis interface
  3. Gm interface
  4. A interface Correct answer.

Explanation

The A interface connects the MSC to the BSC and carries both traffic and signalling, historically over SS7-based signalling. The Abis interface sits between the BSC and the BTS.

Question 38Telecom / Network Engineering (general technical section)

Which GSM logical channel carries the broadcast system information that an idle mobile needs before it can access the network?

  1. FACCH
  2. SDCCH
  3. SACCH
  4. BCCH Correct answer.

Explanation

The broadcast control channel continuously transmits cell identity, frequency and access parameters so that idle mobiles can camp on the cell and decode how to request service. It is a downlink-only common channel.

Question 39Telecom / Network Engineering (general technical section)

In WCDMA, what is the main purpose of fast closed-loop power control on the uplink?

  1. To combat the near-far problem by adjusting each mobile's transmit power Correct answer.
  2. To synchronise the frame numbering of the base station
  3. To equalise the path delay of all users
  4. To allocate orthogonal spreading codes

Explanation

Because all users share the same frequency in WCDMA, a mobile close to the base station would otherwise swamp weaker signals; fast power control commands each mobile to adjust its power so received levels are equalised. This mitigates the near-far problem and improves capacity.

Question 40Telecom / Network Engineering (general technical section)

Which 3GPP release first introduced the IP Multimedia Subsystem as an overlay for delivering voice and multimedia over a packet core?

  1. Release 5 Correct answer.
  2. Release 97
  3. Release 99
  4. Release 8

Explanation

Release 5 added the IMS architecture, allowing operators to offer SIP-based voice and multimedia services over the packet-switched domain. Release 99 defined the original UMTS radio access, while Release 8 introduced LTE.

Question 41Telecom / Network Engineering (general technical section)

In an LTE network, which node performs ciphering and header compression for user-plane packets while the mobile is attached?

  1. MME
  2. Packet Data Network Gateway
  3. eNodeB Correct answer.
  4. Serving Gateway

Explanation

The eNodeB terminates the PDCP protocol, which provides ciphering and robust header compression for user-plane data over the radio link. The core nodes handle mobility anchoring and IP address allocation instead.

Question 42Telecom / Network Engineering (general technical section)

Which optical phenomenon limits the maximum unrepeated span length because it makes the received pulse overlap with neighbouring pulses?

  1. Chromatic dispersion Correct answer.
  2. Modal noise
  3. Rayleigh backscatter
  4. Polarisation-mode dispersion

Explanation

Chromatic dispersion arises because different wavelengths travel at different velocities in the fibre, spreading each pulse in time until adjacent pulses overlap and cause intersymbol interference. Dispersion compensation or narrower linewidth sources extend the reach.

Question 43Telecom / Network Engineering (general technical section)

In a fibre-optic link, what does a link power budget of 28 dB with a total loss of 24 dB imply?

  1. A margin of 4 dB remains for ageing, repairs and temperature effects Correct answer.
  2. The link exceeds the maximum allowed loss and cannot be commissioned
  3. The transmitter output must be reduced by 4 dB
  4. The receiver is saturated and requires an attenuator

Explanation

The power budget is the difference between transmitter output and receiver sensitivity, and subtracting the total fibre, splice and connector loss leaves a system margin. A positive margin of 4 dB means the link works with headroom for future degradation.

Question 44Telecom / Network Engineering (general technical section)

Which statement about a microwave line-of-sight link is correct?

  1. The first Fresnel zone should be at least 60 percent clear of obstructions Correct answer.
  2. Fresnel zone clearance is irrelevant below 10 GHz
  3. Rain attenuation is highest at frequencies below 2 GHz
  4. The antenna height must be reduced to avoid ground reflection entirely

Explanation

For negligible diffraction loss, at least 60 percent of the first Fresnel zone radius should be unobstructed along the path. This keeps the received field close to free-space conditions.

Question 45Telecom / Network Engineering (general technical section)

A satellite in a geostationary orbit introduces roughly what one-way propagation delay to a ground station?

  1. About 12 ms
  2. About 12 s
  3. About 120 ms Correct answer.
  4. About 1.2 s

Explanation

A geostationary satellite sits about 35,786 km above the equator, so the slant range is roughly 36,000 km and the one-way delay is about 120 ms at the speed of light. A round trip through the satellite is therefore around 240 to 280 ms.

Question 46Telecom / Network Engineering (general technical section)

Which antenna parameter describes the ratio of the power radiated in the strongest direction to that of an isotropic radiator?

  1. Beamwidth
  2. Voltage standing wave ratio
  3. Directive gain Correct answer.
  4. Radiation resistance

Explanation

Directive gain compares the peak radiated intensity of an antenna with that of an isotropic radiator fed with the same power. When antenna losses are included, the same ratio becomes the power gain.

Question 47Telecom / Network Engineering (general technical section)

In a cellular network, what happens to the carrier-to-interference ratio when the cluster size is increased while cell size and transmit power stay fixed?

  1. It increases because co-channel cells are farther apart Correct answer.
  2. It becomes undefined because frequency reuse is no longer possible
  3. It stays unchanged because reuse distance and cluster size scale together
  4. It decreases because more cells share the spectrum

Explanation

The reuse distance grows with the square root of the cluster size, so a larger cluster pushes co-channel interferers farther away and raises the carrier-to-interference ratio. The trade-off is fewer channels per cell and lower capacity.

Question 48Telecom / Network Engineering (general technical section)

Which protocol carries signalling between a softswitch and a media gateway in a next-generation network, allowing the gateway to report events and receive connection commands?

  1. BICC
  2. RTP
  3. H.248 / Megaco Correct answer.
  4. SIP

Explanation

H.248, also known as Megaco, is the media gateway control protocol through which a media gateway controller creates, modifies and deletes terminations and receives event notifications. RTP and SIP handle media transport and session signalling respectively.

Question 49Telecom / Network Engineering (general technical section)

In a telecom installation, which earthing arrangement connects the equipment metalwork directly to earth while the neutral is earthed at the supply transformer only?

  1. TT with a local earth electrode and no supply earth
  2. TN-C-S with combined neutral and earth in the final circuit
  3. IT with an unearthed supply and insulation monitoring
  4. TN-S with separate neutral and protective earth conductors Correct answer.

Explanation

In a TN-S system the protective earth conductor runs separately from the neutral back to the source earth point, so equipment metalwork has a direct low-impedance path to earth. This gives predictable fault-loop impedance for protective devices.

Question 50Telecom / Network Engineering (general technical section)

Which standard specifies Power over Ethernet with up to 30 W delivered at the powered device, commonly used for IP phones and access points?

  1. IEEE 802.3af
  2. IEEE 802.3at Correct answer.
  3. IEEE 802.3ad
  4. IEEE 802.3ah

Explanation

IEEE 802.3at, known as PoE+, delivers up to 30 W at the powered device over two pairs, compared with about 12.95 W for 802.3af. It supports devices such as pan-tilt cameras and dual-radio access points.