Digital and Data Comunications (C8 Past Board: Excel)

ECE Board Exam April 2001
Determine from the following, the term used to described the ratio of transmission rate to its minimum bandwidth which is also used to compare the performance of one digital modulation technique to another.
Information capacity

ECE Board Exam November 2000
A process of exchange of predetermined codes and signals to establishe a connection
Handshake

ECE Board Exam April 2000
These are rules in data communications intended for establishing data links and message interpretation.
Protocols

ECE Board Exam November 1999
In telecommunication, what do we call the difference in the voltage levels between a driver and a terminator?
Noise Margin

ECE Board Exam April 1999
A network interconnection facility, which is used to interconnect networks whose architecture are entirely different, is called _________.
gateway

ECE Board Exam November 1998
Main basic components of a data communications are composed of the following:
Transmitter, channel and receiver

ECE Board Exam April 1998
A device that connects two dissimilar networks and performs the protocol conversion.
Gateway

ECE Board Exam November 1997
Operating method in which the transmission is made alternately in each direction of a telecommunication channel. 
Half-duplex operation 

ECE Board Exam April 1997
Transmission sent in both directions simultaneously.
Duplex

ECE Board Exam November 1996
A system that performs parallel-to-serial and serial to parallel conversion of data link
DTE

ECE Board Exam March 1996
A word in telegraphy consist of __________ characters plus a word space.
7 and 1/2


ECE Board Exam April 2001
Technique used in teleprinter terminal that utilizes chemically coated paper where characters are printed.
Electro thermal printing

ECE Board Exam November 2000
Bit rate of a telecommunications carrier T2.
6.312 Mb/s


ECE Board Exam April 2000
A process of sending data in computing technology by asking each remote computer terminal one ata a time if such a computer terminal has data to send.
Polling

ECE Board Exam November 1999
What do you call the definite time interval it takes to a key the slave station by the master in operating the long range navigational equipment or loran?
Time delay

ECE Board Exam April 1999
What does the elastic store referred to in the time division multiplex system used in fiber optic? 
Holding memory 

ECE Board Exam April 1998
_________ is more prevalent in analog signals that have sleep slopes or whose amplitudes vary rapidly. 
Slope overload 

ECE Board Exam April 1998
Is the total useful information processed or communicated over a specific amount of time.
Throughput

ECE Board Exam November 1997
The series of periodically recurrent pulses is modulated in amplitued by the corresponding instantaneous samples.
PAM

ECE Board Exam April 1997
Full duplex transmission means
Two way simultaneous transmission

ECE Board Exam November 1996
The line control unit (LCU) operates on the data in digital form.
Data terminal equipment (DTE)


ECE Board Exam March 1996
The number of voice band channels in a master group per CCITT standard is
300

ECE Board Exam April 2001
Which of the following topology is normally used in system network architecture topology providing order of structure?
Bus


ECE Board Exam November 2000
Which of the following is referred to the SYN character of ASCII code?
16H

ECE Board Exam April 2000
Why is parallel transfer method in data transmission faster that serial?
Bits are transferred simultaneously

ECE Board Exam November 1999
In an open architecture concept of data communication, one of the following is not a function of a control layer.
Integrity of data

ECE Board Exam April 1999
What is the function of the network layer in computer communications?
Congestion control

ECE Board Exam April 1998
Which of the following term best described the overload distortion?
Peak Limiting


ECE Board Exam November 1998
Which of the following refers to full duplex transmission?
Two way simultaneous transmission

ECE Board Exam November 1997
A digital carrier facility used to transmit a DS1 - formatted signal at 1.544 Mbps.
T1

ECE Board Exam April 1997
Transmission system for a multidrop network.
Polling


ECE Board Exam November 1996
The line control unit (LCU) operates on the data in digital form.
Data terminal Equipment

ECE Board Exam March 1996
The expander ina companding device provides _____________
less amplification for low signal levels

ECE Board Exam April 2001
How would you determine if data transmission in computers and terminals is/are done in parallel transfer?
If group of bits move over several lines at the same time.

ECE Board Exam November 2000
How are the variations of the transmitted photograph in terms of brightness and darkness converted into voltage variations?
Through photodetector

ECE Board Exam April 2000
In data transmission technology signals such as voice or radio are binary transmitted over a cable known as ____________.
baseband signal

ECE Board Exam November 1999
Mode of communication system where both sides of the system wait for their turn to transmit at a time?
Half duplex

ECE Board Exam April 1999
Why is it that almost all switching-type integrated data communication circuit are called digital?
They process digital information

ECE Board Exam November 1998
__________ is the method encoding audio signals used in US standard 1,544 kbits/s 24 channel PCM system.
Mu-law

ECE Board Exam April 1998
Which of the following described the very early standard that defines binary digits as space/mark line conditions and voltage levels?
V.1

ECE Board Exam November 1997
12 voice channels are sampled at 8000 sampling rate and encoded into 8-bit PCM word. Determine the rate of the data stream.


ECE Board Exam April 1997
Synchronous modems cost more than asynchronous modem because
they have clock recovery circuits

ECE Board Exam November 1996
Codes must be
agreed upon in advance between sender and receiver.

ECE Board Exam March 1996
One character or a sequence of characters forming a part, or the whole of a message with a specific meaning.
code

ECE Board Exam April 2001
One of the data terminal devices that was invented to replace the Morse code telegraphy
Teleprinter

ECE Board Exam November 2000
__________ is a group of bits that acts as a single unit of information such as a letter or numeral.
Byte

ECE Board Exam April 2000
Transmission of information through a communication modem is intended to transmit digital information over which of the following types of communication medium?
Analog


ECE Board Exam November 1999
Which of the following refers to a network facility used to physically interconnect distinct networks in computer technology?
Bridge

ECE Board Exam April 1999
Communication through the use of a modem, is transmission of _______ data information in ______ medium.
digital, analog

ECE Board Exam November 1998
Refers to an address that identifies a server on the network and a particular document on the server.
Uniform resource locator

ECE Board Exam April 1998
One of the following stands for SONET acronym in telecommunication.
Synchronous Optical Network

ECE Board Exam November 1997
The sinusoidal carrier is pulsed so that on of the binary states is represented by a carrier while the other is represented by its absence.
ASK

ECE Board Exam April 1997
What equation defines the composition of an ISDN basic access line?
 2B + D

ECE Board Exam November 1996
Quantization noise is caused by
the approximation of the quantized signal

ECE Board Exam April 2001
Referred as a modem that is capable of sending and receiving fas as well as data transmission.
ARQ

ECE Board Exam November 2000
An equipment in data communication which is referred to as a source of information to be transmitted at one end and the sink which receives the information at the other end.
DTE

ECE Board Exam April 2000
In computer communication the term RS-232C is referred to as ____________.
serial interface standard

ECE Board Exam April 1999
Kinds of information transfer in digital communication where the bits comprising one character are sent in sequence one at a time.
Serial transmission

ECE Board Exam November 1998
Who is responsible in the correctness and accuracy of transmitted information content over a data communication?
The transmitter and receiver

ECE Board Exam April 1998
Term for the transmission of printed pictures by radio?
Facsimilie

ECE Board Exam November 1997
Determine the dynamic range for a 10-bit sign magnitude code.


ECE Board Exam April 1997
Modem is referred to as _________
Data Communication Equipment

ECE Board Exam November 1996
What is the principal difference between asynchronous and synchronous transmission?
The clocking is derived from the data in synchronous transmission

ECE Board Exam March 1996
What is the IBM's asynchronous data link protocol designation?
83B

ECE Board Exam April 2001
The term used to receive a data file from a remote computer is called __________.
downloading

ECE Board Exam November 2000
Which of the following best described the primary source of errors in the transmission of data over telephone networks?
Crosstalk

ECE Board Exam April 2000
An IT network which interconnects local area network over a broad graphical area.
Wide are network

ECE Board Exam April 1999
Refers to the PCM transcoder which translates voice-encoded signals between different digital formats.
XCBR

ECE Board Exam November 1998
How do you transmit through multiplexing, a thousand of voice channel information over a single fiber optic using one wavelength?
Time division


ECE Board Exam April 1998
Known as the data transfer scheme that used handshaking principle.
Synchronous data transfer scheme

ECE Board Exam November 1997
A coherent binary phase shift keyed BPSK transmitter operates at a bit rate of 20 Mbps with a carrier to noise ratio C/N of 8.8 dB. Find Eb/No.


ECE Board Exam April 2001
Which of the following modulation technique render the amplitude of any of its sidebands dependent on the modulation index?
Frequency modulated

ECE Board Exam November 2000
What do you call a system having a single communication channel that is shared by all machines on a network?
Broadcast system

ECE Board Exam April 2000
What is the baseband frequency of standard FDM basic supergroup?
312 to 552 kHz

ECE Board Exam April 1999
Refers to transmission of two sets of voice signals or other information through two different wavelengths.
Frequency division multiplex

ECE Board Exam November 1998
Which of the following is not referred to as data equipment?
Modem

ECE Board Exam April 1997
What is the reason why companding is employed in PCM systems?
To protect small signals in PCM from quantizing distortion

ECE Board Exam November 1996
How would one squeeze more channels of communication into TDM frames of standard length?
Shorten the time delay for each channel

ECE Board Exam March 1996
The standard that specifies a balanced interface cable that will operate for rates up to 10 Mbps with a span distances up to 1200 m.
RS - 422A

ECE Board Exam April 2001
Speed of data transmission is referred to baud rate which refers to changes in symbol per second as ________. frequency and phase changes.
time

 ECE Board Exam November 2000
In facsimile, how are variations in picture brightness and darkness converted into voltage variations?
with a photodetector

ECE Board Exam April 2000
Network protocol developed by US Defense Department which permits the exchange of traffic between two stations without any prior call set-up.
Internet Protocol

ECE Board Exam April 1999
Type of transmitting two or more channels of voice signal or other information in fiber optic communications in a selected interval of micro or milliseconds, the data or channels being received at their own time slot.
Time-division multiplexing

ECE Board Exam November 1998
The conversion of digital into analog for purposes of training into telephone line is done through ______.
Modem

ECE Board Exam November 1997
Used for time division multiplexing
Pulse Modulation

ECE Board Exam April 1997
What is framing?
Is concerned with the boundaries between characters


ECE Board Exam November 1996
When one station is degnated as master and the rest of the stations are considered slaves message handling is __________.
Polling

ECE Board Exam April 2001
How would you differentiate timing and framing in data transmission?
Timing concerned with individuals bits while framing is to boundaries between characters.

ECE Board Exam November 2000
One of the following refers to the standard procedure for asynchronous to synchronous conversion.
V.14

ECE Board Exam April 2000
Which of the following refers to facsimile?
The transmission of printed pictures for permanent display on paper

ECE Board Exam April 1999
Type of transmission in which each transmission is individually synchronized, this is normally done through the use of start and stop elements.
Asynchronous transmission

ECE Board Exam November 1998
In communications, the transmission of binary signals will require __________
more bandwidth that analog

ECE Board Exam April 1998
Detrmine from the following the basic mode of transmission system in the public data network in which data are transferred from the source to the network and from the network to the destination in the frame format.
Packet Mode

ECE Board Exam November 1997
The difference between the original and reconstructed signal gives rise to
quantizing noise

ECE Board Exam April 1997
The method of determining the bandwidth of any process system is _______.

Spectral Analysis

ECE Board Exam November 1996
RS-232, RS-449, RS-530, V.24, and X.21 are examples of ________.
standards for interfaces between terminals and modems

ECE Board Exam March 1996
One type of pulse communications systems uses pulse that appear as a group, and which vary in number according to the loudness of the voice. This type of pulse modulation is called
pulse duration modulation

ECE Board Exam April 2001
What kind of recording is used in facsimile?
Electrothermal recording

ECE Board Exam November 2000
How would you isolate data communications faults in a basic error determination technique?
Carry out loop back test

ECE Board Exam April 2000
Which of the following describes its system services control point, logical units and physical units as network addressable units in a data network?
System network architecture

ECE Board Exam April 1999
Where does harmonics in a square wave of a simple signal transmission belong?
Odd

ECE Board Exam November 1998
In telecommunications when we call data communications it means the transmission of ________
Computer data

ECE Board Exam April 1998
These are used to connect non-ISDN equipment to ISDN line.
Terminal adapters

ECE Board Exam November 1997
Modulation in which no signal is present between pulses.
Pulse modulation

ECE Board Exam April 1997
It is a protocol use to connect the other packet switching network.
X.75

ECE Board Exam November 1996
What is the data rate of the ISDN BAsic access B channel?
64 kbps

ECE Board Exam March 1996
According to the Nyquist theorem, the sampling rate that can be used in a PCM system is _____ the highest audio frequency.
twice

ECE Board Exam April 2001
_________ is one of the many electronic equipments referred to as a data terminal equipment.
Computer printer

ECE Board Exam November 2000
Method of a telecommunications operation where transmission can be made simultaneously in both direction of a channel.
Duplex operation

ECE Board Exam April 2000
What refers to breaking up the data into blocks with some bounded size?
Segmentation

ECE Board Exam April 1999
A device that is used to permit an equipment with non-ISDN interface to be connected to the digital network.
TA

ECE Board Exam April 1997
Slowest communications hardware product.
Asynchronous

ECE Board Exam November 1997
For a sample rate of 40 kHz, determine the maximum analog input frequency


ECE Board Exam November 1996
Pulse carrier at the ratio of 8000 pulse/sec is amplitude modulated by an analog signal, this type of modulation is
PAM

ECE Board Exam March 1996
What is one principal difference between synchronous and asynchronous transmission?
The clicking is derived from the data in synchronous transmission

ECE Board Exam April 2001
This a fast computing machine with large amount of secondary storage to which other computer machine in the network have access for data storage and retrieval purposes.
Mainframe

ECE Board Exam April 2000
A connector that has the lowest loss at ultra high frequency
Type-N connector

ECE Board Exam April 1999
A data communications network desiigned to provide two-way communications between a large variety of data communications terminal equipment within a relatively small geographic area.
Local area network

ECE Board Exam November 1998
Is individual signal for a handshake from the DCE to the DTE in response to an active condition for the request to send a signal.
Clear to send

ECE Board Exam April 1997
Highest theoretical frequency that can be processed at a sampling rate (fs) without aliasing.
Folding frequency

ECE Board Exam November 1996
A seven-bit character can represent one of _______ possibilities.
128

ECE Board Exam March 1996
What is the number of pins in the RS-232C interface?
25

ECE Board Exam April 1997
Data is directly on transmission cable.
Baseband

ECE Board Exam November 1996
Digital transmission provides a higher level of signal quality than analog transmission because
repeaters regenerate digital pulses and remove distortion.

ECE Board Exam March 1996
What is the transmission rate of system for transmitting the output of a microcomputer to a line printer operating at a speed of 30 lines/minute? Assume that the line printer has 8 bits of data per character and prints out 80 characters/line.


ECE Board Exam November 1998
In what form does the information of data communications is transmitted between two points?
Binary form

ECE Board Exam April 1997
A source code whose average word length approaches the fundamental limit set by the entropy of a discrete memoryless source.
Huffman code

ECE Board Exam November 1996
A ___________ interconnects LAN having identical protocols at the physical and data link layers.
Bridge

ECE Board Exam April 2001
What is the system that process both digital and analog quantities?
Hybrid system

ECE Board Exam March 1996
Communications code is __________.
agreed upon in advance between sender and receiver


ECE Board Exam April 1997
Gateway can interconnect LANs that have _______ protocol and formats.
totally different

ECE Board Exam November 1996
An invitation from the primary to a secondary to transmit a message.
Polling

ECE Board Exam March 1996
Which of the following pulse modulation system is analog?
PWM

ECE Board Exam April 2000
In spread spectrum transmission, which type of modulation is normally often used with direct-sequence?
PSK

ECE Board Exam November 1999
Device that comply with the ISDN network interface and be connected directly to the digital network.
TE1

ECE Board Exam April 1999
Two or more LANs linked together over a wide geographical area.
WAN

ECE Board Exam November 1998
All bits in a character are sent and received ______ in serial port.
one at a time

ECE Board Exam April 1997
Steps to follow to produce PCM signal.
Sampling, quantizing, and coding


ECE Board Exam November 1996
The tranformer signal coding method for T1 carrier is
bipolar

ECE Board Exam March 1996
In ______ transmission, a unique SYN character is transmitted at the beginning of each message.
synchronous

ECE Board Exam April 1997
Transmission sent in both directions simultaneously.
Duplex

ECE Board Exam March 1996
Binary communications systems are better because
the components are simpler, less costly and more reliable

ECE Board Exam November 1996
Multiplexing scheme used by baseband transmission.
TDM

ECE Board Exam March 1996
The correctness and accuracy of the transmitted message content is
determined by the sender and receiver.

ECE Board Exam November 1996
Digital modulation technique used in modems.
PSK

ECE Board Exam March 1996
Data switching systems
improve the efficiency of data transfer

ECE Board Exam November 1996
Multiplexing in a time division multiplexer occurs based upon
the position of data within a frame

ECE Board Exam March 1996
The process of assigning PCM codes to absolute magnitudes.
Quantizing

ECE Board Exam November 1996
Ethernet is baseband system using CSMA/CD operating at
10 Mbps

ECE Board Exam March 1996
Asynchronous protocol is
character oriented

ECE Board Exam November 1996
The primary purpose of data modem is to
interface digital terminal equipment to analog communication channel

ECE Board Exam March 1996
_________ is a device in data transmission to interface a data terminal equipment to an analog transmission line
Modem


ECE Board Exam November 1996
A quadrature signaling have ______ possible states
4

ECE Board Exam November 1996
Rules governing the transmission of digital information
line protocol

ECE Board Exam November 1996
The standard ASCII
has 132 characters including 32 control characters.

ECE Board Exam November 1996
Basic speed rate of digital system
64 kbps