Quiz 06: Digital Selective Calling (DSC)

1. Which internationally recognized frequency is designated for automated DSC distress, urgency, and safety calling within the maritime Medium Frequency (MF) band?

2182.0 kHz 2187.5 kHz 4125.0 kHz 156.525 MHz

Correct Answer: B. 2187.5 kHz is the specific international MF frequency dedicated exclusively to automated DSC digital alerting. (2182.0 kHz is for voice traffic).

2. How many unique High Frequency (HF) channels are internationally grouped and set aside specifically for global DSC distress and safety alerting?

Two channels Three channels Five channels Seven channels

Correct Answer: C. There are exactly five designated HF DSC distress frequencies distributed across the 4, 6, 8, 12, and 16 MHz bands to manage changing day and night ionospheric conditions.

3. Which HF DSC distress frequency is monitored continuously by major shore facilities because it acts as the primary baseline channel regardless of daylight shifts?

4207.5 kHz 6312.0 kHz 8414.5 kHz 16804.5 kHz

Correct Answer: C. 8414.5 kHz serves as the primary, highly reliable intermediate channel for multi-band HF DSC watchkeeping receivers worldwide.

4. What specialized transmission format option should an operator select if an HF DSC distress call must be broadcast across all five safety channels in rapid succession?

Group Alert scanning file Multi-frequency scan or 'Distress Multi-Call' profile Geographical area routing loop Duplex link sweep toggle

Correct Answer: B. Selecting a multi-call setting directs the radio hardware to fire digital data packets sequentially across all 5 HF safety frequencies, maximizing the chance of interception.

5. What type of technical modulation is structurally utilized to send automated digital selective calls over MF and HF frequencies?

Phase Modulation (PM) voice carrier Frequency Shift Keying (FSK) or Audio Frequency Shift Keying (AFSK) Amplitude Modulation (AM) voice grid Continuous Wave (CW) manual telegraphy

Correct Answer: B. DSC uses precise digital data shift keying modulations to cut through atmospheric static and background noise much better than clear voice signals.

6. If an MF or HF DSC alert lists an emergency voice follow-up frequency of 4125 kHz, what mode should the radio operator set on their single-sideband (SSB) transceiver?

Lower Sideband (LSB) Upper Sideband (USB) Amplitude Modulation Equivalent (AME) Wideband Frequency Modulation (WFM)

Correct Answer: B. International maritime rules require all voice operations within the MF and HF bands to use Upper Sideband (USB) mode.

7. When receiving a long-range HF DSC distress alert from a distant ocean zone, what is the mandatory waiting period before a ship station may consider sending a manual acknowledgment?

30 seconds 1 minute 5 minutes 15 minutes

Correct Answer: C. International rules mandate a 5-minute pause to let professional, high-powered shore stations intercept and acknowledge the distress call first.

8. What occurs if a shipboard operator clicks 'Acknowledge' via DSC to an incoming MF/HF digital distress call without authorization?

It prints out a routing coordinate map automatically. It tells the sender's radio to stop its automatic distress transmission loop, potentially silencing their cry for help before shore responders track them. It shifts the local transmitter into high-speed data mode. It alerts nearby aircraft automatically.

Correct Answer: B. A digital DSC acknowledgment cancels the target radio's automated repeat cycle. If sent by a ship out of range, it can accidentally silence the alert before rescue centers receive it.

9. What specialized addressing structure allows an operator to direct an MF/HF DSC call to all vessels navigating inside a specific, defined ocean territory?

Individual MMSI telephone routing Geographical Area Call (using latitude and longitude coordinates boundaries) Group Fleet serial entry file Closed User Group encryption lock

Correct Answer: B. Geographical Area Calling lets an operator target an alert to any radio currently located within specified boundary coordinates.

10. Which international regulatory framework defines the technical performance requirements for MF and HF DSC watchkeeping receivers?

Local Yacht Club by-laws IMO Global Maritime Distress and Safety System (GMDSS) provisions Standard commercial marine insurance policies State maritime recreation agencies

Correct Answer: B. GMDSS international treaties standardize DSC equipment tiers to ensure reliable safety systems worldwide.

11. What action must be taken if an operator accidentally triggers an automated distress alert on the HF DSC frequency 8414.5 kHz?

Turn off the radio system and keep it powered down indefinitely. Cycle power to clear the automated transmission loop, then broadcast a voice cancellation message on the matching HF safety voice frequency (8291 kHz) directed to 'All Stations'. Send a second digital alert with a 'Normal' status modifier entry block. Transmit a text email message using satellite terminals.

Correct Answer: B. False alerts must be canceled by turning off the loop, switching to the matching voice channel (8291 kHz for the 8 MHz band), and broadcasting a formal voice cancellation to all stations.

12. Which of the following is an official HF DSC distress and safety frequency?

4125.0 kHz 6215.0 kHz 16804.5 kHz 12290.0 kHz

Correct Answer: C. 16804.5 kHz is the correct DSC digital signaling frequency in the 16 MHz band. The other options are HF voice safety frequencies.

13. When setting up a 'Routine' individual test call to a coast radio station via an HF DSC console, what parameters should be configured?

Select 'Distress' priority on high-power voice settings. Input the shore station's specific 9-digit coast identifier (00XXXXXXX) and select 'Safety Test' or 'Routine Call' options. Target a random geographical area block boundary link. Program the system to auto-repeat every 30 seconds indefinitely.

Correct Answer: B. Routine testing requires inputting the station's specific coast station MMSI (beginning with 00) and selecting the 'Test' function to prevent disrupting emergency monitoring.

14. Why is ionospheric frequency selection critical when initializing a long-range HF DSC alert transmission?

Lower frequencies transmit much better during broad daylight hours. Radio wave propagation changes with solar activity; higher frequencies work best over long distances in daylight, while lower bands work better at night. High frequency signals travel through underwater currents. Antenna lengths automatically change physical dimensions based on the frequency selected.

Correct Answer: B. Matching frequency selection to solar cycles ensures long-range signals successfully skip off the ionosphere to reach distant receivers.

15. What type of follow-up communication mode is standard after an initial MF/HF DSC 'Routine' call is accepted by another vessel?

Morse code telegraphy key entries Single Sideband (SSB) Upper Sideband (USB) radiotelephony voice on an agreed working frequency Automated commercial satellite email transmissions High-speed digital facsimiles

Correct Answer: B. After the initial digital connection is confirmed via DSC, operators switch to standard SSB voice on an agreed working channel for their conversation.