This is the Section 2 Module 4 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 4
181. Sound provides all sorts of information, what information is related to mental processes of knowledge, reasoning, memory, judgement and perception?
182. What increase in sound level is commonly perceived by most people?
ANSWER: 6 to 10 dB
183. At what loudness level do pitch (in mels) and frequency (in hz) are numerically equal?
ANSWER: 40 dB
184. A __________ is essentially a cell site (shelter) that is mounted on a flatbed tractor-trailer used for emergency purposes
185. This fix tuner is designed to provide just the exact selectivity required to pass both the IF signals?
ANSWER: SAW (Surface Acoustic Wave)
186. Single pulses that can travel through a medium with no dispersion.
187. It is a unique address for a pager
188. Transmission of brief text message, such as pages or email, by cellular radio or PCS.
ANSWER: Short messaging service
189. In cellular or PCS system, connecting a mobile to two or more base stations simultaneously is called
ANSWER: Soft hand-off
190. It is a number that identifies a mobile phone in a cellular system; the mobile telephone number.
ANSWER: Mobile identification number (MIN)
191. In cellular phone, a memory location that stores the telephone number(s) to be used on the system.
ANSWER: Number assignment module (NAM)
192. In the AMPS system, a number transmitted by the base station to identify the system operator.
ANSWER: SID (system identification number)
193. Code which describes the maximum power output of a cellular phone
ANSWER: Station Class Mark (SCM)
194. In a Medium earth orbit (MEO) satellite, A satellite in orbit at a distance above the earth’s surface of approximately
ANSWER: 8,000 to 20,000 km
195. It is the change in direction of polarization of signals passing through the ionosphere.
ANSWER: Faraday rotation
196. A metal object threaded into a waveguide to add capacitance or inductance.
ANSWER: Tuning screw
197. In a microwave tube, any device that cause a wave to propagate at less than the speed of light, so that the electron beam and the wave move at approximately the same speed
ANSWER: Slow-wave structure
198. It is the method of providing high-speed data transmission on twisted-pair telephone lopps by using high frequency carriers.
ANSWER: Asymmetrical digital subscriber line (ADSL).
199. In a klystron, it is a cavity that velocity-modulates the electron beam.
200. It is a circuit for digitizing voice at a low data rate by using knowledge of the way in which voice sound are produced.
201. It is an oscillator whose frequency is controlled by a binary number written to an internal register.
ANSWER: Numerically controlled oscillator
202. It is a colloquial term used to describe additional side frequency produced by overmodulation or distortion in an AM system
203. A signal consisting of two audio frequencies not harmonically related, used to test single sideband transmitters
ANSWER: Two tone test
204. These are now being used to “sign” important documents that are sent electronically
ANSWER: Digital signature
205. Cable-television systems reduce losses by moving UHF signals to the VHF range. They use frequencies
ANSWER: between channel 6 and 7 and above channel 13
206. It is a low-level signal in a telephone receiver deriving from the transmitter in the same instrument. It assures the user that the system is working
207. Why is a Smith chart circular?
ANSWER: Because it is a convenient way to represent the fact that impedances on a transmission line repeat every one-half wavelength
208. What characteristic of solitons makes them interesting for long-distance fiber optic transmission?
ANSWER: Solitons can propagate for very long distance without dispersion
209. What would be the most important advantage of converting the entire telephone system, including local loop, to the fiber optics?
ANSWER: Fiber would allow almost unlimited bandwidth, enabling one cable to carry all needed information services to the home
210. What feature of SONET allows data stream with different clock to be synchronized?
ANSWER: The payload pointer allows synchronization by indicating the start of a data frame
211. The use of Solitons and heterodyne reception may allow fiber optics to operate with much higher data rates and over longer distances without repeaters than any other system now in use.
212. Why can AM radio stations often be received at distances beyond the horizon?
ANSWER: Ground waves follow the curvature of the earth and ground wave can propagation is possible at AM broadcasting frequencies.
213. Why is antenna height important for line-of-sight propagation?
ANSWER: Greater antenna height increases the distance to the radio horizon
214. What is the main advantage of fiber optics in LANs compared to twisted pair wiring?
ANSWER: Fiber allows for much longer distances between nodes that can be used with twisted pairs.
215. What is downtilt and why is it often used for cellular base stations?
ANSWER: Downtilt involves shifting an antenna pattern so that the major lobe is at an angle below the horizontal. It can be used to reduce the range of a base station to reduce interference.
216. What radio system was developed to provide high speed packet data access for the GSM channels
217. The most ambitious of the proposed LEO systems.
ANSWER: Teledesic System
218. Why are soft hand-offs not possible with the GSM and TDMA systems?
ANSWER: Because these systems use different frequency channels in adjacent cells so it is not possible to communicate through more than one call site at a time
219. Why are geostationary satellites unsatisfactory for communication from regions near the poles of the earth?
ANSWER: The angle of elevation to the satellite is too low to be practical in these regions.
220. It is a receiver in which that signal is amplified at its original frequency before demodulation
ANSWER: TRF (Tuned-radio-receiver)
221. The pulses in the vertical blanking interval of a video that create interlaced scan.
ANSWER: Equalizing pulses
222. What connector is popular in attaching test instruments like oscilloscopes, frequency counters, spectrum analyzers, etc?
223. In a klystron, it is a cavity that removes some of the energy from the electron beam and transfers it in the form of microwave energy output.
224. What connector is popular in attaching test instruments like oscilloscopes, frequency counters, spectrum analyzers, etc?
225. It is the velocity modulation of a electron beam
226. What is IMT2000 Stands for?
ANSWER: IMT stands for International Mobile Telecommunications, and 2000 refers both to the approximate implementation date and to the fact that the proposed system will operate at about 2000 MHz
227. IMT2000 Maximum data rate for mobile user in high speed vehicles is
228. IMT2000 Maximum data rate for mobile user in for pedestrian or perhaps slow moving vehicles is
229. IMT2000 Maximum data rate for stationary user is
230. It is the only way to achieved a wider aspect ratio with the current systems is to use fewer active scan lines
231. MPEG-2 compression begins by reducing the number of bits required to transmit a reference frame. This is done using an algorithm called
ANSWER: Discrete cosine transformation (DCT)
232. What video standard deals with low data rate video such as are often found in CD-ROMs, and on the internet?
233. The standard for terrestrial digital television transmission is called:
234. It is a special cable that consist of two parallel wires with a grounded shield around them. It is sometimes used for gigabit Ethernet.
ANSWER: Twinax cable
235. Ethernet system that uses a special “thick Ethernet”.
ANSWER: A standard classical
236. Another problem with Baudot is that an error that is interpreted as a FIGS character can cause all the following information to be interpreted as numerical until the next LTRS character occurs. To reduce this problem, most modern system use technique called
ANSWER: unshift-on-space (USOS)
237. Each block of data is preceded by an eight-bit pattern called a flag, which signals the start of a frame. In SDLC and HDLC the flag consists of the bit sequence
238. The IBM token-ring network uses twisted-pair wiring and can operate at either __________.
ANSWER: 4 Mb/s or 16 MB/s.
239. The IBM token-ring network could support how many nodes with special data grade shielded twisted-pair wiring?
ANSWER: 260 nodes or 72 nodes using telephone twisted-pair wiring
240. Method of data compression by encoding the length of string of ones or zeros instead of transmitting all the one or zero bits individually.
ANSWER: Run-length coding