This is the Section 2 Module 7 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 7
361. Where is the location of the Global Positioning System (GPS) Master Control Station and GPS Operations Center and the US Naval Observatory Alternate Master Clock used to synchronize GPS satellite time?
ANSWER: Schriever Air Force Base (formerly Falcon Air Force Base) in Springfield, Colorado
362. It was established by Ericsson, Sony Ericsson, IBM, Intel, Toshiba, and Nokia, and later joined by many other companies.
ANSWER: IEEE 802.15.1 (Bluetooth)
363. When was Bluetooth implemented/ introduced?
ANSWER: 1998
364. It is an adjustment of two or more tuned circuits so that they can be tuned simultaneously with one adjustment.
ANSWER: Tracking
365. Who is known as the father of WiFi?
ANSWER: Vic Hayes
366. What is the formula for rems?
ANSWER: rems = rbe x rad
367. It defines physical specifications communications protocol standards for the short-range exchange of data over infrared light, for uses such as personal area networks (PANs).
ANSWER: IrDA
368. In TV system, the color level control is in the __
ANSWER: BPA
369. What is the advantage of Doherty linear?
ANSWER: high efficiency
370. What carrier shift results with insufficient grid excitation to a grid modulated stage?
ANSWER: positive
371. What is the third layer of the OSI protocol model which set up the path to transmit data between terminals and arranges data into packets?
ANSWER: network layer
372. What is the popular fiber optics cable with glass core and plastic cladding called?
ANSWER: plastic clad silica (PCS)
373. What are the two functions of a buffer amplifier?
ANSWER: amplify and isolate
374. What is the combine mixer and LO that uses 1 transistor or tube or both?
ANSWER: autodyne converter
375. What is the function of a hybrid in the telephone handset?
ANSWER: decrease in microphone signal in phones
376. Which of the following are parts of the network interface card?
ANSWER: Both BND connector and RJ 45 connector
377. In what two systems in the voice transmitter can speech processing be used?
ANSWER: AF and RF
378. What is the maximum recommended length of RS232 cable?
ANSWER: 50 ft
379. What is the advantage of using hub over direct interconnection?
ANSWER: it's easy to move computers
380. What is the main advantage of GPRS?
ANSWER: it does not require a connection
381. 3G wireless system was introduced in what year?
ANSWER: 2001
382. What is the accuracy of LORAN C long range navigation hyperbolic radio navigation system?
ANSWER: 1/4 of mile absolute and less than 100 ft relative
383. The range of human hearing can form how many octaves
ANSWER: 10
384. In delta modulation, what normally causes error in the received signal
ANSWER: slope overload
385. It is a ferrite which is the inductive element of this tuned circuit is actually the receiving antenna.
ANSWER: Loopstick
386. It is a Modulation technique used for North American TDMA cell phone and PCS systems.
ANSWER: Pi/4 DQPSK
387. The phase detector will generate a control voltage, which will cause the VCO frequency to change until it is exactly that of the external input signal.
ANSWER: Acquisition of phase lock
388. To avoid error and confusion, LAN software make sure that data on the server that is being changed by one station is not simultaneously read by another.
ANSWER: Record locking
389. 10BaseT (T for twisted) system is restricted to a length of __________
ANSWER: 100 m
390. The inductive element of the tuned circuit is actually the antenna which is called __________.
ANSWER: ferrite loopstick
391. Power could be coupled into and out of the waveguides using ___________ in the guide.
ANSWER: Probes, loops, or holes
392. Waveguide are a very practical means of transmitting electrical energy at microwave frequencies, as they have much lower losses than coaxial cables. They are not very useful at lower frequencies
ANSWER: because they must be too large in cross section.
393. In a very small network using only two terminals, It is possible to connect the computers to each other directly without a hub. This requires a special cable called a
ANSWER: crossover cable
394. It is a transmitter power amplifier stage immediately before the output stage.
ANSWER: Intermediate power amplifier (IPA)
395. It is a filter that can pass (or reject) a fundamental frequency and its harmonics.
ANSWER: Comb filter
The interleaving of luminance and color signals conserves bandwidth but causes interference between two signals.
396. It results from the luminance component interfering with the color signal. It occurs whenever there is diagonal detail in the picture, and get worse with motion. It is visible as spurious color in the picture.
ANSWER: Cross luminance
397. It is caused by color information being interpreted as luminance, causing structure of fine dots
ANSWER: Cross color
398. The disadvantage of a client-server approach is that it ties up one computer as the network file server.
399. It can amplify an optical signal without converting in into electrical form.
ANSWER: Optical amplifiers
400. Fiber optics has greatly increased both capacity and reliability of submarine cables.
401. The stability of a superheterodyne receiver depends directly on that of a __________.
ANSWER: local oscillator
402. Contention
Definitions (1)
It is a condition that arises when two or more data stations attempt to transmit at the same time over a shared channel, or when two data stations attempt to transmit at the same time in two-way alternate communication. Note: A contention can occur in data communications when no station is designated a master station. In contention, each station must monitor the signals and wait for a quiescent condition before initiating a bid for master status.
Definitions (2)
It is a competition by users of a system for use of the same facility at the same time. Synonym: access contention.
403. It is a standardized, if relatively lossy, file format for transporting, storing, and/or displaying data representing still images and graphical data
ANSWER: J-PEG or JPEG (Joint Photographic Experts group)
404. Three point tracking is achieved with ___________.
ANSWER: padder capacitor
405. In a ferrite, rotation of axis of rotation of the electron.
ANSWER: Precession
406. The operating frequency of klystrons and magnetrons is determined by
ANSWER: cavity resonators
407. Coax is not used beyond frequencies of about __________ GHz.
ANSWER: 6
408. The beamwidth of a helical antenna is usually in the range of __________.
12 to 45 degrees
409. Analog telephone signals are frequency-division multiplexed using SSBSC AM, with approximately ANSWER: 4 KHz of bandwidth allocated to each voice channels.
410. Digital telephone signal are time-division multiplexed with a data rate of
ANSWER: 64 kb/s per voice channels
411. Parametric amplifier (Paramp):
It is an amplifier that
(a) Has a very low noise level.
(b) Has a main oscillator that is tuned to the received frequency.
(c) Has another pumping oscillator of a different frequency that periodically varies the parameters, i.e., the capacitance or inductance, of the main oscillator circuit, and
(d) Enables amplification of the applied signal by making use of the energy from the pumping action.
Note: Paramps with a variable-capacitance main-oscillator semiconductor diode are used in radar tracking and communications Earth stations, Earth satellite stations, and deep-space stations. The noise temperature of paramps cooled to the temperature of liquid helium, about 5 K, is in the range of 20 to 30 K. Paramp gains are about 40 dB.
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