This is the Section 2 Module 5 of the compiled Communications Coaching Materials taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies (EST), Communications Books, Journals and other Communications References. This particular Coaching Notes in Communications Engineering has random Questions and Answers in random topics. Make sure to familiarize each questions to increase the chance of passing the ECE Board Exam.
Communications Engineering Coaching: Section 2 Module 5
241. A data compression scheme that replaces repeated characters or bit patterns with a code indicating character or pattern and the number repetitions
ANSWER: Run-length coding
242. Lossless compression scheme generally looks for redundancies in the data for instance the string of zeros can be replaced with a code that tells the receivers the length of the string. What do you call this technique?
ANSWER: Run-length coding
243. Encryption of data is important to ensure its privacy. It is most commonly achieved by using a public-key encryption to transfer a key to be used in __________.
ANSWER: a symmetrical private key
244. It is the deviation of a wave as it passes an obstacle that passes through a small aperture
ANSWER: Diffraction
245. It is a television receiver design that uses mixing between the picture and sound carriers to generate the sound intermediate frequency.
ANSWER: Intercarrier sound
246. A spurious pattern or other distortion in a facsimile record copy caused by unwanted modulation products arising from the transmission of a carrier signal, and appearing in the form of a rectified baseband that interferes with the lower sideband of the carrier.
ANSWER: Kendall effect
Note: The Kendall effect occurs principally when the single-sideband width is greater than half of the facsimile carrier frequency.
247. It is the interchanging of the frequencies of carrier channels to accomplish specific purposes, such as to prevent feedback and oscillation, to reduce crosstalk, and to correct for a high frequency-response slope in the transmission line.
ANSWER: Frequency Frogging
248. About the Low earth orbit (LEO) satellite, the first problem is less important then it might seem. Shorter range results in much less propagation loss and removes the requirement for highly directional antenna. This makes antenna tracking less critical. In any case, if the antenna is mounted on a moving vehicle or person the direction to the satellite is constantly changing. Even with geostationary satellite. When real time communication is required, the only way to address the second problem is to use a __________ containing more than one satellite.
ANSWER: Constellation
249. It is the cheapest LAN configuration, and if one station fails the whole system fails.
ANSWER: Ring topology
250. A network station which all station attach to a common cable and the fastest LAN configuration.
ANSWER: Bus topology
251. Cellular radios that use FM has a maximum deviation of ___________.
ANSWER: +-12kHz
252. In the GSM system, a telephone number that us unique to a given user, worldwide
ANSWER: International Mobile Subscriber Identification (IMSI)
253. A frequency multiplier can be created by tuning the output circuit of a class C amplifier to a
ANSWER: multiple of the input frequency
254. The __________ is a variation on the discriminator. It greatly reduces sensitivity to amplitude variations, at the cost of a 50% reduction in output voltage.
ANSWER: radio detector
255. It is the time between the instant of going off-hook and the instant of receiving a dial tone.
ANSWER: dial-tone delay
256. The interfering beat frequency of 920 KHZ is between 3.58 MHz color sub carrier and ___________.
ANSWER: 4.5 MHz inter carrier sound
257. What does aspect ratio means?
ANSWER: ratio of screen width to its height
258. What happens in balance modulation if it is not properly balanced?
ANSWER: the carrier is transmitted
259. What is the sound characteristics related to a sonic time pattern?
ANSWER: Rhythm
260. In telephony, M88 loading coil (88mH loading coil) is placed at an interval of ___________ feet.
ANSWER: 9000
261. In telephony, the cable used for costumer loop in telephone exchanges, which has a round trip loop resistance of 170 ohm / 100 miles is __________.
ANSWER: AWG No. 22
262. Wireless internet service provider (WISPs) use WiFi technology to provide internet access to airports, hotels, convention centers, coffee shops, and other public places. When users are within the range of an antenna, WISPs offer access to the internet at speed up to __________Mbps.
ANSWER: 11
263. What service is provided by broadcast ISDN (B-ISDN) providers that offer a means of bidirectional end-to-end data transmission, in real time, between two subscribers or between a subscriber and the service provider called?
ANSWER: Conversational service
264. What is the data rate of WiMax?
ANSWER: 11 Mbps
265. What is the bit rate of GPRS?
ANSWER: 172.2 kbps
266. What is the other name of MPEG 7?
ANSWER: Multimedia Content Description Interface
267. Among the following materials used by the acoustic engineers, which has the highest absorption coefficient for sound wave?
ANSWER: Celotex
268. Which camera tube that has minimum lag?
ANSWER: Plumbicon
269. It reduces reverberation in studios by means of loudspeaker feedback system.
ANSWER: Ambiophony
270. If a broadcasting station is transmitting, but not modulating, what will be heard in the receiver of that tuned frequency?
ANSWER: Nothing
271. a closet which is terminating facilities which consists of key telephone system services, central offices, stations, and PBX, but there is no key telephone circuitry present
ANSWER: Satellite Closet
272. April 2002, the IEEE standard 802.16 Broadband Wireless Access (BWA) is __________.
ANSWER: WiMax
273. What is the GPRS uplink data rate?
ANSWER: 14 Kbps
274. What is the gamma of the picture tube of a TV
ANSWER: 2.2
275. A microwave tube that is a linear wave tube in which the interaction between the beam and the RF field is continuous is called
ANSWER: traveling wave tube
276. What is the optimum volume per person in churches?
ANSWER: 7.1 - 9.9
277. What is the optimum volume per person in cinemas?
ANSWER: 3.1
278. What is the South Korean version of WiMAx?
ANSWER: WiBRO
279. What is the other name for 3G?
ANSWER: UMTS
280. In GPS navigation system, how many satellites are there in one orbital plane?
ANSWER: 4 Satellites
281. What is the velocity factor of a coaxial cable wire?
ANSWER: 0.6 to 0.8
282. What is the typical range of velocity factor in transmission lines?
ANSWER: 0.5 to 0.9
283. Ribbon microphone is what type of microphone?
ANSWER: Pressure-gradient microphone
284. What is the exact frequency of the color burst signal?
ANSWER: 3.579545 MHz
285. What is the velocity of sound in wood?
ANSWER: 3300 m/s
286. In cellular radio, one base station cost approximately
ANSWER: $500,000 to $750,000
287. What is the disadvantage of using a fiber optic cable that is made of glass?
ANSWER: Brittleness
288. What is the advantage of using a fiber optic cable that is made of glass?
ANSWER: Less attenuation/ losses
289. GPS is a satellite navigation system consisting of 24 satellites. When was the first satellite was launched?
ANSWER: 1978
290. What are the microphones that has high Z output?
ANSWER: crystal, electret, condenser
291. What are the microphones that has low Z output?
ANSWER: dynamic, ribbon, carbon
292. What is the diagonal screen size of picture tube of 19CP4
ANSWER: 19 inches
293. It is one of the PCB techniques used to create special microwave transmission lines in which a flat conductor sandwiched between two ground planes
ANSWER: Stripline
294. What is the oldest semiconductor device used in microwave transmissions?
ANSWER: Point Contact
295. Antenna beam on a Geostationary Satellite that is adjusted to cover the whole earth.
ANSWER: Hemispheric Beam
296. In what year does the first satellite SPUTNIK I was launched?
ANSWER: 1957
297. All colors on the color test signal are modulated 75% except
ANSWER: gray
298. Satellite subsystem that monitors on board temperature and battery voltage ,then transmits this data back to ground station
ANSWER: TTC
299. Which of the following coaxial cable connectors is called the UHF connector?
ANSWER: PL 259
300. Which coaxial cable connector is least expensive and is widely used for TV sets, VCRs and Cable TV?
ANSWER: F type connector
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