Wireless MOB devices

“Man overboard” is one of the most dreaded calls that any mariner will ever hear. The impact of the cry is chilling, especially if you are offshore sailing shorthanded, or standing a lonely mid-watch on a black, rain-streaked night. Weather, sea conditions, position and time of day all figure into the odds of a successful man overboard (MOB) rescue, but the fact is that a crewman’s life is in grave danger if he is not located and recovered as quickly as possible. One type of device that uses the latest in technology to increase the odds of recovery are wireless MOB devices. These units can signal a receiver unit that a crewmember has gone over the side and also help in the process of homing in on the victim.

The key component to MOB prevention and recovery, of course, is crew training. Crewmembers must take appropriate safety precautions, such as using jacklines when on deck or in the cockpit, and wearing a harness and an inflatable PFD equipped with whistle and strobe. In addition, voyagers should follow common sense procedures like never going forward at night without advising the helmsman or another crewmember. Crewmembers need to know how to quickly deploy MOB devices, such as man overboard modules (MOMs), life rings, throwropes, etc. They must also be able to quickly establish the position of the MOB, stop the boat and safely execute a recovery maneuver.

Unfortunately, crew training and the use of vessel-mounted signaling and recovery aids can only go so far in preventing a MOB tragedy. If a crewman goes overboard without being quickly noticed, every minute that goes by reduces the chance of survival.

A new generation of crew safety devices works to improve those chances of survival through the use of wireless technology.

Traditional signaling systems like the MOM, personal ELTs and handheld devices like the rescue laser flare are now being com­pli­­mented by personal man over­board alarms that can easily be worn by all crew­mem­­bers. These systems employ a wire­­less, battery-operated trans­mitter or trans­ceiver that is usually worn by the crew­member as a pendant or affixed as a wrist or armband. They can also be worn on a belt, safety harness or a PFD. Depending on the manufacturer, these personal devices signal an alarm at the master unit aboard the vessel that audibly notifies the rest of the crew that someone is missing or in some sort of distress. Most of the devices have a manual activation button that will also trigger the system. This feature enables crew to respond and assist in other emergencies such as fire, medical emergencies and flooding. Some of these     systems integrate the master unit with the ship’s GPS and chartplotter through an NMEA connection, and some even disable the boat’s engine when activated. Depending on the system and network integration some MOB wireless systems are expandable to support crews in excess of 18 people.

 Even among the most prudent of mariners mishaps will occur, and these new wireless devices are a welcome addition to any vessel’s safety locker. They are but one more tool that can be used to further ensure crew safety and prevent a needless loss of life at sea. What they are not is a substitute for proper training and vigilance.

LifeTag Wireless Man Overboard Monitoring System:
The Raymarine personal wireless man overboard system consists of a pendant that broadcasts a unique code back to a base station telling it that the wearer is safe. If the signal between the pendant and the base station is broken as a result of an MOB situation (water degrades the signal, as does the distance between the victim and the boat – typically 30 feet) an alarm is sounded. The LifeTag pendant also incorporates a manual activation button enabling the wearer to call for assistance in case of emergency.

LifeTag can also trigger the man overboard alarm in Raymarine SeaTalk-compatible chartplotters, radars and other instruments. In addition to an alarm, an integrated system will provide a GPS position at the time of the activation and make the target a waypoint on all SeaTalk connected devices. Critical search and rescue data will also be included, such as elapsed time in the water (or since activation), water temperature, and bearing and range back to the MOB.

The base unit can be powered by either 12-volt DC or the SeaTalk network. The base station also has outputs for alarm sirens. The wireless crew pendant is supplied with a wrist strap and has a tricolor LED for status feedback. It uses replaceable CR2 lithium batteries (estimated life – 200 hours) and powers on and off automatically.

Mobilarm, Ltd., of Western Australia, manufactures several crew monitoring systems. All are based upon pendant-style personal transmitters (PTX) and a multifunctional base station receiver. The core of the system is a wireless, waterproof rechargeable transmitter that is worn by each crewmember. In the absence of a signal the base station sounds an alarm and the vessel’s position is logged using GPS data. The company manufactures three systems: 720i, 7200 and 7600.

The 720i system is best suited to vessels with crews of up to six persons. It is comprised of an antenna and an audible/visual alert panel and rechargeable PTX pendants. The unit is NMEA compatible with most chartplotters and can accommodate additional alarms and an engine shut off. The company’s 7200 and 7600 systems use a graphic display screen and GPS data to guide the vessel back to the position of the MOB. The screens display bearing and pictorial directions back to the MOB. The systems also provide secondary relays to additional alarms, devices and engine shut-offs. The 7600 is equipped with an active GPS receiver. The 7200 is not GPS-equipped but can send waypoint data to any NMEA-compatible chartplotter. Both systems can accommodate up to 18 transmitters and have an operating range of about 100 feet.

Alert 2 Man-Overboard Alarm:
The Alert 2 Man-Overboard Alarm is based on a water-activated transmitter that transmits a 418-MHz coded signal when immersed for one second. When the shipboard receiver acquires the coded signal it triggers an audible alarm. The receiver can also be connected to an NMEA-compatible chartplotter for determining the position of the MOB. The receiver can also be wired to shut down the engine. The Alert 2 systems are simple and robustly built. The transmitters are manually activated and have an effective operating range of about one mile. They are powered by two 3.6-volt lithium batteries and have a battery shelf life of five years. (Note: batteries should be replaced after emergency use.) There is no limit to the number of transmitters that can be used. An optional automatic direction-finder antenna can also be used to locate the MOB’s Alert 2 signal by sweeping the horizon.

Mobwatcher is a radio-controlled device dedicated to engine shutdown. The system is simple and comprised of two components: a personal, battery-operated transmitter and a vessel-mounted receiver. When the signal between the transmitter and receiver is broken the vessel’s engine is automatically shut down. Once the engine is shut down the system does not require that the radio signal be re-established to restart it. Mobwatcher is manufactured in Sweden and has received the endorsement of a number of European marine insurance companies that offer a premium discount for its use. The system does not provide any position data or audible alarm and is primarily suited to single-operator power boats like rigid inflatables, open patrol boats, etc.

ACR Mini B 300 ILS H2ON:
ACR’s Mini B 300 ILS H2ON is a floatable, water-activated 121.5 MHz EPIRB with an in-line speaker that emits audio warble to confirm activation and transmission of a distress signal or to notify of accidental activation. An LED indicator also confirms transmissions. The device is designed to be used with ACR’s Vecta2 direction finder for homing in on 121.5 MHz transmitters. The Vecta2 will home in on any 121.5 MHz transmissions. ACR also produces a Mini B 300 unit that is not water activated. Both Mini B devices incorporate a durable double-braided antenna that can be folded without distortion when being stowed. The units are compact and robustly built of fiber-reinforced polycarbonate. Both feature user-replaceable, easy-to-obtain lithium camera batteries.

Sea Marshall Self-Managed Rapid Alert and Alert & Locate MOB Systems:
The heart of the Sea Marshall system is a personal locator beacon that transmits a 121.5 MHz homing signal that is received by a dedicated shipboard base station or by other SAR teams homing in on the 121.5 MHz frequency. The company offers two types of personal beacons, PLB8-LR SOS, which features manual or automatic (immersion activated), or the manually-activated PLB8 SOS unit. Both devices are waterproof and are powered by lithium batteries that must be returned to the manufacturer for replacement.

The Sea Marshall man overboard base unit SAR Finder 1003 continuously monitors three channels (121.5 MHz, 121.65 MHz and 121.775 MHz) and produces an audible crew alarm when the beacon is activated. The base unit also incorporates a 15° interval direction finder. 

By Ocean Navigator