Some Frequently Asked Questions about Man Overboard Systems

Do I have to sign a lengthy airtime £ contract for using the Sea Marshall® system ?

No. There are no hidden charges.

My customers keep asking me for a 406MHz PLB for Man Overboard use ?

406 MHz PLBs are satellite based non-automatic beacons, primarily designed for land use.
Because 406 MHz PLBs are not fully automatic which means that if you fell overboard and were knocked unconscious or the water was so-cold that you could not use your arms and fingers properly from cold shock response then you would be unable to activate and deploy your 406MHz PLB. Another big disadvantage of 406 MHz in the context of Man Overboard Rapid Alert & Locate is that because they are satellite based it can take up to 90 minutes for a signal to be received by a satellite and forwarded to a ground station. It can take many more hours before any Search & Rescue vehicles could have even been launched by which time the person in the water could be in real trouble. In the context of Man Overboard Survival, the time factor is critical, a delay of minutes can mean the difference between life and death. 406MHz PLBs can only give a satellite accuracy to within 6km square and they rely on an integral low powered 121.5Mhz transmitter to allow SAR to home into their position.

Why is 121.5MHz the Best Frequency for MOB systems?

By transmitting on 121.5MHz you have the added back up of being able to be tracked electronically by Coast Guard Search & Rescue should you require extra outside assistance…this is because 121.5MHz is the Internationally Recognised Search And Rescue Homing frequency.

I’ve heard that 121.5MHz is going to be switched off…what does this mean and how will this affect my Sea Marshall® system?

There is a lot of confusion about 121.5MHz at the moment, the frequency of 121.5MHz is and will always be the Internationally Recognised Search And Rescue Homing Frequency. Sateliite coverage of 121.5 MHz through the Cospas-Sarsat satellite system will be switched off in the coming years, this does not however affect in any way non satellite based locally managed Search & Rescue Systems such as the Sea Marshall® Self Managed Maritime Survivor Locating Devices. In fact it has the positive affect of reducing false alerts. The following is a quote from the COSPAS SARSAT website:

What is the difference between a Sea Marshall® Alert & Locating System and a proximity alert Man Overboard Alert system which uses a constant radio link from a pendant with a receiver on the boat?

With a Proximity MOB Alert system the only information given when an Man Overboard incident occurs is the GPS position of the boat at the time the incident occurred this is not enough. With the Sea Marshall® Self Managed MOB Alert & Locate System you are given an immediate warning of a Man Overboard incident combined with the ability to track and rescue the Man Overboard at day or night time even if they have drifted well away from the boat. As an example in an incident which took place in Spain in the early part of 08 the surviving crewmen from a sinking trawler who were wearing Sea Marshall® Alerting Units fitted into lifejacekts were tracked from 30 miles by SAR helicopters. The pendants used in proximity based systems do not transmit a homing signal which means if you drift out of sight you are lost there is now way of tracking you other than by sight.

• Proximity Alert MOB systems use pendants which require recharging for lengthy periods of time at very short intervals, usually every 24 hours.
• Proximity Alert MOB systems can only be used on smaller vessels due to radio blind spots causing false activations.
• Should a crew member fall overboard and become tapped next to the boat in a line or net than the Alarm will not be activated because you are still within the proximity field.
• Cannot give the Direction of a Man Overboard in the water.
• Cannot be Located or tracked by Search & Rescue Services.