1. What frequency does this system operate on and why?
The Sea Marshall® Alerting Units transmit on the Internationally recognised Emergency Homing Frequency of 121.5 MHz. This gives the user the added advantage that if the person wearing the Alerting Unit goes out of range of the Base Unit, or for some reason the boat with the Base Unit onboard is unable to perform a rescue then the Local Emergency Services can take over the Rescue and Track the 121.5 MHz signal with their own onboard Base Unit/ Radio Direction Finding equipment. 

2. From what range can a signal from a Sea Marshall® Alerting Unit be picked up from?

3. Can the System be used to cover a Jetty/Harbour or remote location ?
Yes, we offer a system with a MOB Alarm Only connected to an External antenna to give greater range, the alarm can then if required be connected to an Auto dialler to send a pre-recorded message if a signal from a Sea Marshall® Alerting Unit is picked up. Base Units with Locating Function can then be fitted to SAR craft, or the local Search and Rescue Authorities can be contacted directly to carry out the rescue operation.

 

4. What applications can the Sea Marshall® system be used for?
 

	…Coastguards, River Pilots, Fire Brigades, Search And Rescue crews…etc.
	…Yachting…Leisure & Professional
	…Diving…Sport & Technical
	…Oil & Gas Industry (Offshore)
	…Aviation, Glider Pilots, Microlites
	…Wind Farms
	…Ports & Harbour Authorities, Jetty Workers, Fish Farms …etc.

5. Why is 121.5 MHz better than other frequencies for Man Over Board Accidents ?
There are some Personal Locator Beacons available which transmit on a satellite frequency of 406 MHz which are being offered for use in the maritime industry. Be aware that these are not Man Over Board Alerting Units…they are not automatic i.e. they cannot activate themselves automatically in water after 15 seconds. The minimum response time for a 406MHz beacon can be up to 90minutes before a search is even initiated. The signal from a 406 MHz Personal Locator Beacon must first be received by a satellite and then relayed down to a ground station which could be a few thousand miles away. From here the ground station must then contact the nearest Search And Rescue Authority and ask them to investigate…all this takes time…and time is in short supply when you are at risk of drowning. It only takes matter of minutes for a Man over Board to have drifted out of sight of the boat, if cannot locate them immediately the chances of finding them at all are very slim. 406 MHz Personal Locator beacons are totally dependant on the person carrying the unit being able to switch it on…a difficult task if you’re unconscious or in Cold Shock response! 406 MHz Personal Locator Beacons are better for Mountain climbing and land use. 

• The minimum Alert time for the fully automatic Sea Marshall® ‘SOS’ Man Over Board Alerting Unit transmitting a signal on 121.5 MHz to a boat fitted with a Sea Marshall ‘SOS’ Base Unit is approx 15 seconds. 

 

 


 

• 406 MHz Personal Locator Beacons are not fully automatic…useless if you are knocked unconscious! 

 
• 406 MHz PLBs must be registered to each person…these mean that they cannot be exchanged amongst crew members who are swapping between being on deck and below. 

 
• Other Alerting Units transmitting on obscure frequencies away from 121.5 MHz cannot be tracked by the Search and Rescue Authorities! Which means that if the person in the water floats out of range of the receiver on the boat then the chances of them being located are dramatically reduced…the search will become visual only which is like looking for a needle in a haystack. 

 
• Proximity Alerting systems, working on frequencies away from the SAR homing frequency, carry the risk of a crew member falling over board and becoming trapped next to the vessel, in a line or net perhaps, and the alarm not being raised because the person has not gone out of the monitored area resulting in drowning. Also such systems are operating on frequencies that cannot be tracked by the Search And Rescue Authorities. 

 
• 121.5 MHz is the only frequency for Man Over Board Alert & Rescue. 

6. Are the crew alerted if a man falls in the water wearing a Sea Marshall® ‘SOS’ Alerting Unit, even if he is unconscious ?

Yes, when a man falls overboard his Sea Marshall ‘SOS’ Alerting Unit will automatically begin transmitting after approx. 15 seconds of continuous immersion. Alternatively the Alerting Unit can be activated manually by pressing the large activation button on the front of the unit.

 

7. Does the Sea Marshall ‘SOS’ Alerting Unit need to be removed from a carrying pouch for it to activate ?

No the Sea Marshall ‘SOS’ Alerting Units are fully automatic. (NOTE: Only the Divers PLB needs to be removed from its carrying pouch, it is manual activation only) 
 

8. How should I wear the Alerting Unit to make sure I get the strongest signal?
 

…an example of a Sea Marshall® Alerting Unit fitted into a lifejacket

9. What are Maritime Survivor Locating Devices / MSLDs ?
 

- Alerting Unit.

 

- Base Unit.

 

 
 
 

10. What are Alerting Units?

A device worn by a person which communicates with a Base Unit to indicate when a Man Over Board Incident has occurred.

11. What are Base Units?

…A device that receives radio signals from one or more Alerting Units to indicate that a person using an Alerting Unit has fallen over board. This can be one of two options: 

1. Man Over Board Alarm Only (Crewguard-121)

 

 
 
 


 

2. Man Over Board Alarm with Locating Function (SARfinder® 1003)

 

 
 
 

…what FUNCTIONS do the Alerting Units (AU) and Base Units (BU) provide
 

Alert -	Alerting Unit (AU) sends out an R.F. (radio) signal to alert the Base Unit (BU).
Alarm -	Base Unit (BU) constantly listens for a signal from an Alerting Unit (AU). If a signal is received by the Base Unit it will provide an on-board alarm to notify the crew of an MOB situation.
Locate -	The Man Over Board Alarm With Locating Function gives crew the ability to locate the MOB.

...Locating Function

12. How accurate is the Sea Marshall® ‘SOS’ Base Unit with Locating Function ?

The SARfinder® Base Unit With Locating Function has a resolution of 10°. The Base Unit will take you straight to the person in the water, day or night. 

13. How Accurate are the Sea Marshall® ‘SOS’ Alerting Units ?

The Alerting units rely on the accuracy of the Base Unit which is being used to locate them. The SARfinder® Base Unit with Locating Function has a resolution of 10°, this Base Unit will take you straight to the person in the water. A SAR helicopter using its own on-board Radio Direction Finder (Base Unit) can get within 1 square metre (On Top) of a Sea Marshall® Alerting Unit. 

14. How long will the Sea Marshall® ‘SOS’ Alerting Unit transmit a signal in a Man Over Board emergency for ?

20 to 30 hours average. 

15. What is the working life of the battery in a Sea Marshall® ‘SOS’ Alerting Unit ?

Unused 10 years. 

16. Can the battery in the Sea Marshall® ‘SOS’ Alerting Units be replaced by the user ?

Yes it is a 9 Volt lithium PP3 battery (except Oil Filled Divers Beacon/PLB8-LD - must be returned to MRT). 

 

17. Can the battery in the Sea Marshall® ‘SOS’ Alerting Unit be checked?

Yes the unit can be tested when switched OFF, the colour of the LED in the antenna will show the status of the battery. 

18. Can the Sea Marshall® ‘SOS’ Alerting Unit be used again once it has been used in a Live Emergency ?

Yes, the Sea Marshall® ‘SOS’ Alerting Units can be used any number of times. Always check the battery status before re-using your Alerting Unit.

19. Can the antenna be removed from the Sea Marshall ‘SOS’ Alerting Unit to allow easy servicing and battery replacement ?

Yes, simply twist and unlock. (expect for Diver/Submariner models which have fixed antennas). Always test the Unit again when the antenna has been replaced. 

 

20. What happens if several crew members fall into the water at the same time ?

The Sea Marshall® SARfinder® ‘SOS’ Base Unit with Locating Function will pick up and display the nearest and strongest signal first, when this person is recovered from the water their Alerting Unit is simply switched off so that the next signal can be tracked. 

21. Can the Sea Marshall® ‘SOS’ Base Units detect when a crewmember of another boat, which is within range, wearing a Sea Marshall® Alerting Unit on 121.5 MHz falls overboard ? 
Yes. 

22. Can the Sea Marshall® ‘SOS’ Man Over Board System be activated accidentally causing a false alert ?

Each Sea Marshall® ‘SOS’ Alerting Unit has a rubber restraining ring fitted around its body. This ring sits either above or below the ready switch to prevent the unit being accidentally switched off or on. The Base Units have a code facility which when selected means the unit will only respond to signal from a Sea Marshall® Alerting Unit. The Alerting Unit must be continuously immersed for approx. 15 seconds for it to begin transmitting which prevents accidental activation from swamping by a wave. 

 

23. How complicated is it to install the Sea Marshall® ‘SOS’ Man Over Board System ?

The system is easy to install with full instructions given. The SARfinder® Base Unit with Locating Function, can be mounted either flush mount, on a trunnion mount (included) or surface mounted. The Unit is fully waterproof IP67. The Crewguard Base Unit Alarm only, is waterproof IP65. The Alerting Units can either be fitted into a lifejacket or worn around the neck. 

24. Can the Sea Marshall® ‘SOS’ Man Over Board System be tested ?

Yes, the Sea Marshall® ‘SOS’ Alerting Unit has low powered self test facility. This signal can be checked on a Base Unit (as per SARfinder® display picture below). 

A test Frequency Alerting Unit is available on 121.65 MHz (rather than 121.5 MHz which is live). This intended to be used for trials and testing purposes for Oil and Gas platforms, Coastguards, professional yacht crews, large leisure yacht crews or who ever may need to perform sea trials. 

25. Can other devices be connected to the Sea Marshall® Base Unit ?

Yes, there is an external relay on all Sea Marshall® Base Units which could be linked into a DSC, GPS, engine cut out switch etc. etc. 

26. Where am I not permitted to use this system ?

The Sea Marshall® system can be used worldwide as 121.5MHz is the Internationally recognised Search And Rescue Homing Frequency. 

27. Does the user require a license ?

This can be added onto your VHF license. 

28. Can the Sea Marshall® ‘SOS’ Alerting Units be incorporated into a lifejacket ?

Yes. A number of lifejacket and survival suit manufacturers now build the Sea Marshall® PLB into their suits and jackets as standard. Example below.