Reviewer in Wire and Wireless Communications System | ECE Board Exam

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(Last Updated On: February 15, 2020)

Review Notes in Wire and Wireless Communications System

This is the Reviewer in Wire and Wireless Communications System as one topic in ECE Board Exam 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 this review notes to increase the chance of passing the ECE Board Exam.

Summary of Important Wire and Wireless Communication Review Notes

10 to 100 μW – typical speech power

The maximum intelligibility for voice frequency is located between 1000 and 3000 Hz

The maximum voice energy is located between 250 and 500 Hz

Volume unit meter – a device used to measure speech volume

By definition, for a sine wave 0 dBm = 0 V.U

Presently, 300 to 3400 Hz is the “standard” frequency bandwidth for voice transmission

AWG # 19 is commonly used wire for subscriber loop design

The resistance limit for No.2 Crossbar Exchange (US) is 1300 Ω

AWG # 26 has typical loss of 0.51 dB/1000 ft

4 kHz is the standard voice channel spacing

Reflectometer is used to measure SWR

Singing – an undesired self-sustained oscillation in a system, generally caused by excessive positive feedback

IF stage increases the selectivity of the circuit in an AM receiver

The sensitivity of radio receiver amplify weak signal and produce a desirable intelligence at the output speaker

Full-duplex transmission means two-way simultaneous transmission

Multi drop line – a line or circuit interconnecting several stations

A passive attenuator is an electronic device which reduce signal strength by a specified amount in dB

Roaming – the signal quality of the cells is constantly monitored by the base station, when the quality of the calls drops below a certain specified level, the base request the MTSO to try and find a better cell site.

MIN – a digital identification associated with a cellular system

Facsimile transmit a standard page of 25 seconds

Electrolytic recording – a kind of recording is used in facsimile

Skewing – a type of distortion a facsimile produces when it becomes out of synchronization

Acoustic coupler – a device that converts electric signal signals into audio signals, enabling data to be transmitted over the public telephone network via a conventional telephone handset

Crosstalk causes a herringbone pattern in facsimile

The capture effect in an FM receiver causes a stronger signal to dominate over a weaker signal on the same frequency

Hybrid circuit – a device that converts a 2-wire circuit to a 4-wire circuit

Decision theory is deciding between a set of hypotheses when given a collection of imperfect measurement

Jaynes maximum entropy principle of a data reduction says that when reducing a set of data into the form of a underlying mode, one should be maximally non-committal with respect to missing data

Estimation is selecting the best value of a parameter from a continuum of possible values when given a collection of imperfect measurements

Discrete channel – combination of modulator, channel, and detector

The frequency band of DECT is 1.88 – 1.90 GHz

Each DECT system can support 12 simultaneous calls

A DECT radio transceiver can assess 120 simultaneous calls at any given time

The AGC voltage of a radio receiver is always DC, but may have either polarity

Concentrator – a switching system that lets a large number of telephone or data processing subscribers use a lesser number of transmission lines or a narrower bandwidth

If you find that an SAW filter output is 6 dB down from the input of a receiver during test, this is normal

A triple conversion superheterodyne receiver, diode mixer stages are operated in the nonlinear region

Leased line – a permanent circuit for private use within a communication network

If two FM signals of different strengths are received on the same frequency only the stronger will appear in the AF output

Cellular mobile system was first operated in 1983

TACS is a cellular system with 1000 channels

Supervisory Audio Tone (SAT) has 6000 Hz frequency

GSM uses GMSK digital modulation technique

The power output of Personal Communications System (PCS) is 10 mW

RG-58 cable has a loss of about 3 dB at cellular frequencies up to 15 feet length

Pilot carrier signals – the signals designed to keep the receivers and transmitters aligned

When a line and a load are match, the reflection coefficient is zero

When line is terminated in an open circuit load, the reflection coefficient is unity

The telephone set is powered by the central office on the ring side at -42 to -52 Vdc

The telephone voice band frequency is from 300 to 3400 Hz

Green wire is used to transmit the signal

The corresponding frequencies for digit 7 in the touch tone telephone is 852 & 1209 Hz

The physical connection between the telephone set and the switching equipment is called the subscriber loop

The local loop of a telephone system is a two-wire or four-wire communication circuit between the customer’s premise and the central office

Dial long lines, voice repeater, and loop range extender are used in long loop design

A two-wire circuit is a circuit usually in the subscriber loop, between the telephone set and the local central office

1 mW is equal to 90 dBm

First selector responds to the request of a subscriber by sending a dial tone

Section – the other name of Class 2 office in the North American Switching Plan

A cell in the cellular telephone system means small area

MTSO is the linking point between cell phone and regular telephone

The typical power output of a cellular phone is 3 W

When a single cell is subdivided into smaller cells the process is called cell splitting

The first cell shape is a circle

In order to provide 100% coverage without overlap, cellular telephone system can use hexagon cell shape, triangle, or rectangular

The beamwidth of the reflector of the receiving antenna in the base station is 60 degrees

A cellular phone operates on full duplex

Cellular phone transmit in the band from 825 to 845 MHz

Cell phone receives in the band from 870 to 890 MHz

The frequency separation between the transmit and the receive channels 45 MHz

For channel 1, transmit/receive frequency is 825.015/870.015 MHz

The number of transmit/receive channels in the cellular system is 666

The transmission range of cellular telephony is generally about 80 km

Large service area is not an advantage of a cellular telephone system

When the message is transferred from one cell site transmitter to another cell site transmitter as the caller crosses a boundary hand off process take place

The sensitivity of a cellular receiver is 50 dB

The frequency deviation of the cellular telephone system is +-12 kHz

Hailing channel is otherwise known as calling channel

Erlang is equal to the number of simultaneous calls originated during a specific hourly period

All of the cell base stations are linked together by MTSO which serves as the central office and management node for the group

Cell site – provides interface between the mobile telephone switching office and the mobile units

A phone call over the cellular network actually requires full duplex channels

Volume – a method of expressing the amplitudes of complex non-periodic signals such as speech

Echo is a signal returned to the talker after making one or more round trips between the talker and the listener

Echo suppressor is a voice operated device that inserts a high loss in the opposite direction of transmission of the talking party

Double spotting is picking up of the same station at two nearby points on the receiver dial

Crosstalk – when one channel picks up the signal carried by another channel

TPS type of connector arrangement wherein a customer may move to another location and still retain the same telephone number

An advantage of sidetone is that is assures the customer that the telephone is working

Half-duplex – radio communications between points using a single share frequency

TDM – the transmission of information from multiple sources occurring on the same facility but not at the same time

When human voice and music are transmitted, the type of communication employed is known as radiotelephony

Printed documents to be transmitted by fax are converted into a baseband electric signal by the process of scanning

Charge couple device is the most commonly used light sensor in a modern fax machine

In FM fax, the frequencies for black and white are 1500 and 2300 Hz respectively

Group 2 fax uses vestigial sideband AM

The most widely used fax standard is Group 3

Group 3 fax uses QAM modulation

Most fax printers are of thermal type

Facsimile standards are set by the CCITT

Satellite weather photos are commonly transmitted by radio fax

The transmission speed of group 4 fax is 56 kbits/s

Mobile telephone switching office is the master control center for cellular telephone system

Each cell site contain a repeater

Trunk – a telephone line connecting two central offices

Cellular telephones use full-duplex type of operation

The maximum frequency deviation of an FM cellular transmitter is 12 kHz

The output power of a cellular radio is controlled by the MTSO

When the signal from a mobile cellular unit drops below a certain level, the unit is “handed off” to a closer cell

In a cellular radio, the duplexer is a pair of sharp bandpass filters

On a telephone system, the loop is open during on-hook condition

For every button pressed on a touch-tone telephone, two audio-frequency tones are transmitted to the C.O.

Erlang B is the traffic model about blocked calls clear condition specified blocking probability

A touch-tone telephone generates 8 audible tone frequencies

935 – 960 MHz – the base-to-mobile frequency assignment of a GSM system

A voice-grade channel is suitable for transmission of signals with a frequency ranging from 300 to 3400 Hz

The bandwidth of cellular CDMA system is 1.23 MHz

A communication link is a channel or circuit intended to connect other channels or circuits

Poisson – block calls held condition specified the held probability at a time period equal to an average holding time

Echo – a wave which has been reflected or otherwise returned with sufficient magnitude and delay for it to be perceptible in some manner as a wave distinct from that directly transmitted

The system used by Personal Communication Network (PCN) is modified GSM

Termination refers to load connected to the output end of a transmission line

The multiple access used by Digital European Cordless Telephone (DECT) is TDMA

Erlang C – blocked calls delay condition specified delay probability

GFSK – the modulation technique used by DECT

A four-wire circuit is used between serving central offices for long-distance connections, with one pair being used for each direction of transmission

Cellular CDMA system uses BPSK modulation

PABX means Private Automatic Branch Exchange

The voted cellular digital standard at TIA is Digital AMPS

The number for channels for Band A and for Band B in Digital AMPS is 416

The mobile-to-base frequency assignment for GSM system is 890 – 915 MHz

The range of a cellular CDMA system is 13 miles

In a cellular system, radio capacity is used to measure the spectrum efficiency

Singing echo is completely out of control

Loop extender increase the battery voltage on a loop and extends its signaling range

Under ordinary circumstances, the CCITT recommends that the number of circuits in tandem must not exceed 12

The system capacity of AMPS is 100,000

NAM means Numeric Assignment Module

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