54 Questions
What is the 4–20 mA signal commonly used for?
Industrial communications standards
What is impedance in the context of electrical circuits?
The opposition a conductor offers to a changing current value
What do standard signals allow manufacturers to do?
Build instruments for a larger group of users
Which digital communication standard is primarily used in process control?
FOUNDATION Fieldbus
What is EBCDIC primarily used for?
Special or graphic characters
What does ASCII use a ninth bit for?
'Odd' parity
What is the purpose of block parity?
Detect errors prior to transmission
Which organization designed one of the first digital communications codes?
'IBM'
What is the difference between ASCII and EBCDIC?
'ASCII' uses a ninth bit for parity and 'EBCDIC' uses blank spaces for special characters.
What does the ITA2 Telegraph Code use for efficiency?
Letter frequencies and compression
What are fieldbuses primarily used for?
Process control
What does the international standard for an industrial fieldbus define?
Eight different fieldbuses
What is the purpose of the block parity character in the transmitted block?
To determine if parity was met for all the characters in the block
In which layer of the OSI model is packet data referred to as frames?
Layer 2
What is the primary purpose of a CRC character in data transmission?
To detect errors in the transmitted data
What is the difference between a checksum and a CRC?
A checksum is used for linear code while CRC is used for cyclic code
What is the purpose of an Automatic Retransmission Query (ARQ) in error correction?
To automatically retransmit the portion of the message that was in error
What is the main function of forward error correction?
To prevent errors in the transmitted data
Why is parity checking considered less efficient than CRC for error detection?
It does not provide as high efficiency in detecting errors as CRC
What happens when there is simplex transmission with regards to error correction?
No error correction is possible in simplex transmission
Which error detection code may be mislabeled as a checksum, but is actually a cyclic code?
CRC-16
What kind of code divides the text bits with a binary polynomial to create a check character?
Cyclic code
In data communications, what are the three modes of transmission?
Simplex, half-duplex, duplex
What are the three types of media used in data communications?
Electrical conductors, light pipes, electromagnetic transmission
What is the purpose of communication?
To transmit data from the source to the destination
What are the possible topologies for data communications?
One-to-one, one-to-many, many-to-many
What is a communications channel composed of?
Hardware configuration or virtual circuit
What are the members of a network likely to have?
Defined relationships with or without ranking
What are the three elements required in any communication?
Sender, receiver, message
What is the organization of data in communication sometimes called?
Data encoding
What are the different types of relationships members of a network may have?
Both ranked and no ranked relationships
What are the two types of communications circuits?
Virtual and hardware circuits
What is the term used to describe a mode of transmission where communication can travel in both directions simultaneously?
Full-duplex
How is a digital signal defined?
With defined discrete states
What is the term used for a continuous signal that represents some other time varying quantity?
Analog signal
What term is used to describe a signal that has the approval of the users and/or a standardization agency?
Standard signal
What term is used to describe a mode of transmission where one speaker communicates at a time?
Half-duplex
What is the term used to describe a binary digit that can be either '1' or '0'?
'Binary' digit
What is the primary function of American Standard Code for Information Interchange (ASCII)?
To represent text using binary digits
Why is 'unidirectional' considered a more appropriate name for the simplex mode of transmission?
'Unidirectional' is less confusing for readers referencing technical data
What term best describes the way data should be organized to yield information usable to humans?
'Human-readable' organization
What term best describes the feature of a digital signal where it has only two defined states?
'Discrete' feature
What is the primary reason the ARQ method will not receive an ACK/NAK on a unidirectional circuit?
Unidirectional circuit prevents the transmission of acknowledgments or negative acknowledgments
What is the main requirement for FEC (Forward Error Correction) to be effective?
Analysis of the communication network's error patterns and design of an error-correcting algorithm
What is the physiological reason behind the protocol of shaking hands when introduced to someone in the United States?
Humans are effectively half-duplex, so shaking hands allows for non-verbal communication
What does 'baud rate' refer to in the context of data communication?
The line modulation rate, representing the number of signal changes per second on the communication medium
Which protocol is characterized by control depending on specific character combinations rather than bit patterns?
Binary Synchronous Communication (Bi-Sync)
What distinguishes bit-oriented protocols from character-based protocols?
Bit-oriented protocols use framing and specific bit patterns for start and end delimiters
What purpose do start delimiters serve in bit-oriented protocols?
They indicate the start of a new frame of information
What is the key characteristic of Bi-Sync protocol's operation?
Its ability to eliminate turnaround time during transmission by using duplex operation
What is the primary distinguishing feature of bit-oriented protocols?
They use specific bit patterns for framing and addressing within the protocol
What is a characteristic feature of framing in bit-oriented protocols?
It involves start and end delimiters, addressing information, sequence numbering, and user data
What was the primary reason behind developing Bi-Sync protocol's duplex operation?
To increase transmission speed by eliminating turnaround time during transmission
What has been the focus of this chapter in terms of introducing foundational concepts?
The basics of data communication and networking
Test your knowledge of analog signals and the 4–20 mA industrial communications standard. Learn about voltage, current, resistance, impedance, capacitive reactance, and inductive reactance.
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