Section-j: mf-hf Equip. And Comms: Key Topic #91: mf-hf arq Operation – op Codes & Procedures:

91J1 What sequence of ARQ codes matches the following: manual over, end of message text, end of connection to land destination terminal?

A. NNNN, KKKK, GA+

B. KKKK, DIRTLX, NNNN

C. +?, NNNN, KKKK

D. +?, . . . . ., BRK+

91J2 What sequence of ARQ codes matches the following: request establishment of a landline, end radio link after traffic is done, request connection for AMVER messages?

A. NNNN, KKKK, AMV+

B. KKKK, BRK+, AMV+

C. BRK+, DIRTLX+, AMV+

D. DIRTLX, BRK+, AMV+

91J3 What sequence of ARQ codes matches the following: Send synoptic weather, switch control from a station currently transmitting over to the receiving station, terminate phasing with coast station.

A. OBS+, +?, BRK+

B. OBS+, WRU then Here is, BRK+

C. OBS+, GA+?, KKKK

D. AMV+, +?, KKKK

91J4 A manual ship-ship ARQ message would typically begin with what sequence of ARQ procedures?

A. Initiate call with CS selcal, observe exchange of answer-backs (WRU-AAB), send message.

B. Initiate call with ship selcal, enter “HERE IS” then “WRU” commands and send message.

C. After phasing with the other vessel, observe exchange of answer-backs (WRU-AAB), send message and then KKKK to end the transmission.

D. After phasing with the other vessel then send GA+? to determine if they are ready to receive your message.

91J5 What sequence of ARQ codes matches the following: shore station indicates it is awaiting instructions from the vessel, vessel requests a live connection to a land telex number, vessel indicates it is done with the coast station?

A. WRU-AAB, DIRTLX, NNNN

B. GA+?, DIRTLX, BRK+

C. GA+?, DIRTLX, KKKK

D. WRU-AAB, DIRTLX, .....

91J6 All country codes which are transmitted by MF/HF SITOR (NBDP) are preceded by which character(s)?

A. 00

B. +

C. 0

D. DIR

Answers: 91J1 - C 91J2 - D 91J3 - A 91J4 - B 91J5 - B 91J6 - C

Section-j: mf-hf Equip. And Comms: Key Topic #92: mf-hf arq Operation–Technical Characteristics:

92J1 Which of the following statements concerning SITOR (NBDP) communications is true?

A. In ARQ, each character is transmitted twice, about 250 milliseconds apart.

B. In ARQ, the "information sending station" will transmit a block of three characters that the receiving station will subsequently acknowledge or request be retransmitted.

C. In ARQ, the "information sending station" transmits a block of three characters twice, about 250 milliseconds apart.

D. SITOR (NBDP) communications can be used to contact a NAVTEX transmitting station when requesting a repeat transmission of a missed NAVTEX message.

92J2 What statement is true regarding the exchange between two parties engaged in SITOR (NBDP) communications?

A. In ARQ, each character is transmitted twice, with the second displaced in time from the first.

B. 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.

C. 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.

D. Broadcasts of Maritime Safety Information, traffic lists, etc. can be copied by the receiving station in ARQ mode.

92J3 Of the following, which is true of SITOR (NBDP) ARQ mode?

A. The acceptance code consists of three characters.

B. A continuous data stream is transmitted.

C. Forward error correction reduces the number of errors.

D. Each data block consists of three characters.

92J4 Which of the following is true of SITOR (NBDP) ARQ mode?

A. This is an interactive mode.

B. Each character is repeated three times.

C. Each character is transmitted twice.

D. This mode is generally used to broadcast messages.

92J5 In ARQ, when the information sending station (ISS) receives a signal that the parity check failed what happens?

A. The next block will be sent.

B. The data link will break.

C. The acknowledge light should illuminate.

D. The last block will be resent.

92J6 Which of the following is true of SITOR (NBDP) ARQ mode:

A. 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.

B. The ship station sends a group of 3 characters twice and then waits for an "RQ" signal to indicate proper receipt before continuing transmission.

C. The Ship station sends each character twice, using a time diversity system to ensure proper parity.

D. 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.

Answers: 92J1 - B 92J2 - C 92J3 - D 92J4 - A 92J5 - D 92J6 - A