7-A-092: MF-HF: ARQ Operation #5: Technical Characteristics
7-92J1:
Which of the following statements concerning SITOR (NBDP) communications is true?
In ARQ, the "information sending station" will transmit a block of three characters that the receiving station will subsequently acknowledge or request be retransmitted.
In ARQ, each character is transmitted twice, about 250 milliseconds apart.
In ARQ, the "information sending station" transmits a bloc of three characters twice, about 250 milliseconds apart.
SITOR (NBDP) communications can be used to contact a NAVTEX transmitting station when requesting a repeat transmission of a missed NAVTEX message.
7-92J2:
What statement is true regarding the exchange between two parties engaged in SITOR (NBDP) communications?
In ARQ, the ISS transmits a block of 3 characters and the IRS checks for parity. If the received block is correct a one-character control signal is sent notifying the ISS to proceed with the next block. If the parity check fails the block must be resent.
In ARQ, each character is transmitted twice, with the second displaced in time from the first.
In ARQ, the "sending" station transmits a block of three characters and the "receiving" station responds with a one character Repeat Request. Following this the "transmitting" station will send a new block.
Broadcasts of Maritime Safety Information, traffic lists, etc. can be copied by the receiving station in ARQ mode.
7-92J3:
Of the following, which is true of SITOR (NBDP) ARQ mode?
Each data block consists of three characters.
The acceptance code consists of three characters.
A continuous data stream is transmitted.
Forward error correction reduces the number of errors.
7-92J4:
Which of the following is true of SITOR (NBDP) ARQ mode?
This is an interactive mode.
Each character is repeated three times.
Each character is transmitted twice.
This mode is generally used to broadcast messages.
7-92J5:
In ARQ, when the information sending station (ISS) receives a signal that the parity check failed what happens?
The last block will be resent.
The next block will be sent.
The data link will break.
The acknowledge light should illuminate.
7-92J6:
Which of the following is true of SITOR (NBDP) ARQ mode:
The ship station sends a group of 3 characters, the shore station checks for proper parity. If parity is OK, the shore station indicates readiness for transmission of the next 3 characters.
The ship station sends a group of 3 characters twice and then waits for an "RQ" signal to indicate proper receipt before continuing transmission.
The Ship station sends each character twice, using a time diversity system to ensure proper parity.
The ship station sends a group of 3 characters, the shore station checks for proper parity and then requests the same group be resent to enable error correction.
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● = Review
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● = Learned
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● = Incorrect answer
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