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Electronic lifelines: MOB insurance

High-tech personal safety devices are making rescues quicker and easier when the unthinkable happens

Accidents happen every day on the water. I’ve had some experience being in the water as the boat appears to get smaller and smaller on the horizon. No one expects to fall overboard and end up in a possible life-or-death situation, but it can and does happen. If the unthinkable took place, would you be prepared?

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There are numerous low-tech products designed to be used in an MOB situation, but the newest electronic alerting technology is designed to make these potentially life-threatening accidents less risky. Several companies have developed electronic safety devices focused on this age-old problem.

AutoTether is a wireless lanyard system that, in its simplest form, will shut down any typical kill-switch-equipped outboard boat if the operator goes overboard. The system eliminates the obtrusive and movement-restricting conventional red kill-switch lanyard. The LifeTag system from Raymarine is a wireless MOB locater that uses an audible alarm to signal the boat and activates the MOB function on compatible SeaTalk-enabled Raymarine chart plotters and networks. ACR’s ResQFix GPS personal locator beacon (with internal GPS) will transmit an MOB’s position and personalized identifier code through the COSPAS-SARSAT satellites, alerting SAR authorities that you need rescue.

This roundup comprises LifeTag, ACR's ResQFix PLB and AutoTether.

I’ve examined these three products on board and at the workbench. Here’s what I found:


I used the AutoTether system aboard my twin-engine Boston Whaler center console, which is equipped with a single kill switch that shuts down both outboards simultaneously through a single lanyard. The AutoTether system consists of a host unit — a self-contained transmitter/receiver — two remote FOBs (personal sensors) worn by vessel occupants, batteries and attachment hardware.

The AutoTether system shuts down the engine if a person wearing a sensor falls overboard.

Using bright, two-color-capable LEDs, the host display indicates system power, alarm condition and reset, along with the number of FOBs that have been switched on. While two FOBs are included with the system, it can monitor up to four per host unit. A 12-inch coiled wire and integral, solenoid-activated, spring-loaded ignition kill-switch clip are designed to replace the red lanyard, which, along with the FOBs, eliminate the hassle of people being physically connected to the boat.

The host unit attaches to the boat’s console using hook-and-loop fasteners, and it needs to be clearly visible to the operator and within 12 inches of the vessel’s emergency kill switch. It measures 3-3/4 by 2-3/4 by 3/4 inches and is water-resistant to 3 feet, so it

shouldn’t be difficult to locate a good installation spot.

FOBs are designated as “operator” (yellow) and “passenger” (white), because they perform different functions. If an operator FOB is submerged for 0.5 seconds, the host triggers the AutoTether audible alarm and shuts off the engines by activating the spring-loaded AutoTether kill switch. If a passenger FOB is submerged, it will trigger only the host unit’s audible and flashing-light alarm. The passenger MOB alarm doesn’t disable the engine, allowing the operator to maneuver and pick up the person who has fallen overboard.

Measuring 3 by 1-1/2 by 3/4 inches — smaller than most cell phones — and weighing 2.15 ounces, the FOBs have detachable clips that can be attached to swim trunks or clothing, but they do not float. Velcro-style straps are also included.

I easily threaded the white passenger FOB to a conventional PFD strap and clipped my yellow operator FOB to the harness of my inflatable PFD. The manual warns against covering an active FOB with clothing, PFD, towel etc., as it may cause signal disruption and inadvertently trigger the alarm. I experienced no signal disruption during my testing.

I appreciate the fact that both the FOBs and host unit are screwed together, requiring a tool to access the batteries. Screws allow for a positive and secure seal without damaging the case halves, as often occurs by using coins or other devices to open cases. The screws are captive in the case to avoid misplacing them, and the thin silicone O-ring has a shoulder to assist in alignment. The included 12 AAA batteries (six in the host, three in each FOB) are good for 150 hours of use, according to the company, and that should get most of us through a full season of boating.

When the host is properly installed and activated, it automatically establishes communication with the active FOBs and continuously monitors each one. The FOBs cannot be turned off manually, which prevents them from being unintentionally disconnected from the system. In an emergency, you can hold the “off” button on the FOB for more than two seconds, activating the AutoTether audio alarm, triggering the spring-loaded kill-switch clip, and shutting off the vessel’s propulsion. That is the only time the white FOB will shut down the engine. Each FOB will shut off automatically after the host is powered down.

So long as the host is mounted within the operator’s line of sight, the alarm-mode LED activation is significant enough to call your attention to the unit. The audible alarm, however, was disappointing. The low volume of 71DBc at three feet is due in part to the buzzer being mounted within the splash-proof enclosure of the host. It’s great that the system is totally self-contained and portable, but I would appreciate a louder internal buzzer that can be clearly heard over engine noise and an auxiliary output that would allow connecting the device to the boat’s horn or other signaling device. More on that later.

Basic system activation, testing and operation are straightforward, but reading the owner’s manual is a must. Aside from the obligatory safety disclaimers and FCC regulations, there are 14 pages of valuable information in the well-written manual.

The host has multiple LED indicators that confirm the status of the system, which FOBs are active, the battery condition, alarm condition, and any system faults. All system indicators are clearly described in the manual, but I would also appreciate a small waterproof “cheat sheet” that quickly guides the infrequent user through setup and decoding the indicator lights in the event of system alarm or fault.

My initial concern with a device such as AutoTether is the potential of inadvertent engine shutdown because of false alarms induced by splashing the FOB. Anthony Viggano, inventor of AutoTether, assured me that more than two years were spent developing the software to assure AutoTether’s reliability, working out such issues as accidental discharge and radio-signal interference. There are more than 3,600 lines of code written into the AutoTether software, and the units have serialized numbering, allowing future software updates.

To confirm the practicality of the FOBs in adverse conditions, I held both FOBs under running water for extended periods without activating the alarm. However, they activated the alarm quickly when totally submerged in water. Viggano says the host and FOB communicate using 16-bit code. Submersion in a large body of water blocks the transmission of data, but the FOB is not activated by brief splashing. When the FOB is hit by a wave, some data is transmitted, but the host knows the FOB is not under water and doesn’t go into alarm mode. The system requires three consecutive missed transmissions of less than 80 percent of code for activation.

After using AutoTether, my thoughts immediately went to how I can adapt it to my diesel trawler, which has no kill switch. And what about a sailboat? All boats and operators can benefit from this relatively inexpensive safety add-on. Viggano has been working on such options, and the company can provide an accessory switch and related circuitry or diagrams that can adapt AutoTether to perform almost limitless alarm responses, such as disconnecting an autopilot, sounding horns and flashing lights. There’s even a version that is connected to a handheld air horn if you’re looking for a really loud alarm.

As a tender anti-theft device, you could place one of the FOBs in your dinghy at night and set the host by your bunk (remember, it’s portable). If someone moves your tender and goes beyond the system range of 150 to 200 feet, the alarm will sound.

AutoTether works as advertised and certainly enhances the safety of the operator and passengers. It’s a cost-effective means of dealing with a potential MOB situation. It operates independently of any other on-board electronics, yet can be incorporated into larger and more complex systems.

AutoTether seems the perfect MOB device for anyone who spends time single-handing. Whether fishing, cruising or taking the kids tubing, knowing that the boat will shut down and be there for you to reboard should you go over the side is a comforting feeling. It is manufactured entirely in Connecticut, and with an office staff of four, including Viggano, you’re certain to speak with someone having firsthand product knowledge should you need assistance.

This retail price is $295 for the standard AutoTether with two FOBs. AutoTether offers a “Solo Fisherman” version with one FOB for $235 and the wireless handheld air horn model for $375. Additional FOBs are available for $69 each. Engine-specific adaptors for the actuator are included. Visit to purchase directly or for a list of retailers.

Raymarine LifeTag

The LifeTag system addresses the MOB situation on a scale geared more toward larger vessels. The system provides not only an audible alert when a person goes over the side, but also SeaTalk integration with Raymarine multifunction displays and instrument systems.

Raymarine's Life Tag provides an audible alert when a person or pet goes over the side.

LifeTag can trigger the automatic MOB function in compatible chart plotters, radars and instruments, providing audible and visual alerts to all stations; record GPS coordinates of the MOB event, making it the target waypoint; and lower the range scale on connected plotter and radar displays. There is also a built-in relay contact for triggering external devices, such as lights or horns.

The basic LifeTag system consists of one base station and two personal pendants, or “tags,” worn by crewmembers. The system has the ability to monitor up to 16 tags and can be further expanded by purchasing additional “repeater” base stations. Each repeater base station added will increase the systems-monitoring capability by 16 crewmembers.

The base station and repeater stations are designed to be surface-mounted vertically and hard-wired, as they require a fused external power source of 8 to 16 volts DC. Each station measures 4-3/4 by 2-3/4 by 1-3/8 inches, with wiring pigtails extending from the lower edge of the plastic housing. Two electrical cables exit the case: the SeaTalk power/data cable and the included remote alarm buzzer pair. Another pair of wires would be required if the 12-volt auxiliary output is used. I would have preferred the option of running the wiring out the back of the base station, which would protect the wiring and provide a more professional-appearing installation.

Installing a LifeTag system interfaced with SeaTalk requires a double pole switch in the SeaTalk cable, while only a single pole switch is required without SeaTalk. Neither switch is provided. The repeater base station must be connected through a SeaTalk three-way connection block (not provided). Wiring and terminations within the base stations use push-in connections that are well laid out.

The base station will emit a chirp when powered up, but there are no visual indicators to confirm operation. This is a critical piece of safety equipment and, as such, I think it should have a readily visible indicator light confirming system status. The audible, remotely mounted “buzzer” provided with the system produced 84DBc at three feet, more than most other on-board alarms.

The plastic buzzer measures 2-1/4 inches in diameter, 1-1/2 inches thick, and includes a small zinc-plated steel surface-mounting bracket and 12-inch wire leads. For a decidedly high-tech system, Raymarine might have given a bit more consideration to its mounting and installation.

The personal tags for the system measure 2 by 2-1/4 by 1 inch, weigh 1.65 ounces, and float. They can be attached to a crewmember’s belt or PFD with the included closed clip, placed in a pocket, or strapped to an arm or wrist with the included hook-and-loop strap. The tags also feature an eye that can be used to attach a lanyard or keychain. I dropped one in a jacket pocket along with keys and completely forgot about it for the afternoon without incurring any false alarms. Each tag is powered by a single CR2 lithium battery that Raymarine says has a 2,000-hour life. The alarm will sound if the tag’s button is held down for five seconds, if the tag is submerged for longer than 10 seconds, or if the tag is out of range of the base unit (approximately 30 feet) for 10 seconds or more.

The Raymarine LifeTag System, with its 16-person capability and electronics interface, can certainly provide MOB alert coverage for an entire family, crew and pets. By providing lat/lon coordinates within seconds of the incident (when interfaced with appropriate on-board electronics), it offers security in knowing you can return to the exact location to retrieve the person. The ability to easily provide MOB monitoring for a large number of people and pets makes the system valuable aboard larger vessels, especially those that already make use of the Raymarine SeaTalk system.

The basic LifeTag System retails for $695, which includes the master base station and two tags. Additional tags are $115 each, and the repeater base station retails for $469.


The ACR ResQFix 406 GPS personal locator beacon is a last-ditch “send in the cavalry” device. The ResQFix PLB does one job, and it’s the one job you’ll need done when everything else fails.

The ACR ResQFix PLB has a 16-channel GPS to transmit the wearer's position, along with their personalized identifier code.

The PLB is manually deployed and activated. With the push of a button, the ResQFix will use its internal 16-channel GPS to acquire and transmit your position, along with your personalized identifier code, through the COSPAS-SARSAT satellites, instantly alerting search-and-rescue forces that you need immediate help. ACR makes it clear that PLBs are not to be misused: “AUTHORIZED FOR USE ONLY DURING SITUATIONS OF GRAVE AND IMMINENT DANGER.”

PLB registration with a “national authority” is mandatory, which in the case of devices purchased in the United States is NOAA ( Required information is clearly marked on the PLB and in the manual; registration is free and can be updated as often as you need. On the registration site you’ll find provisions for change of ownership or contact information if you lend the PLB to a friend.

The manual provides a telephone number for the U.S. Air Force Rescue Coordination Center to report a false alarm, but unfortunately it doesn’t appear on the unit. There are severe penalties for not immediately reporting a false alarm, so I’d want that number handy. However, the PLB’s design makes it nearly impossible to activate the unit unintentionally. The on/off button is covered until the antenna is deployed.

The ResQFix PLB weighs 10 ounces, measures just under 6 inches tall, 2-1/4 inches wide and 1-1/2 inches thick. It will float, but only with the aid of its included neoprene flotation pouch. A very effective belt clip and an 18-inch bungee lanyard are included, so there are options for attaching it to yourself. I attached the ResQFix to my belt during a full day of working in the shop. The belt clip worked exceptionally well. The unit stayed put, and I actually forgot I was wearing it.

The PLB is waterproof to 16-1/2 feet for an hour. Battery life exceeds the required 24 hours for a Category 1 PLB and, according to ACR literature, typically tops 40 hours at minus 4 F, longer in higher ambient temperatures.

The PLB includes a self test of internal circuitry, battery voltage and power, 406 MHz transmission, and GPS acquisition. ACR recommends performing the simple test monthly. The PLB’s condition can be confirmed without deploying the antenna and without risk of activating the distress signal. To activate the unit in an emergency, unfasten the antenna from the case, move it into the upright position (exposing the on/off button), and press the button for one second.

What I truly like about PLBs is they are personal devices. It seems that I spend a lot of time aboard boats that I don’t own, and many have marginal safety equipment. I always take along my inflatable PFD and a belt pouch with a small amount of traditional MOB gear.

ACR is a company with worldwide recognition and acceptance. Its PLBs are used by the U.S. military, Coast Guard and NATO, to name a few. With a retail price of $599, it is worth serious consideration.

Include these items for added safety

Having some basic gear both on the boat and on your person can prevent an inconvenient MOB situation from becoming a life-threatening emergency. I’ve listed some of the items I carry in addition to those required by Coast Guard regulations.

For example, when wearing my inflatable PFD, I attach a small gear pouch (think fanny pack) to its waist strap. That pouch includes several signaling options for both day and night use. My traditional offshore Type1 PFD has two pockets that hold the same gear. This may sound like overkill, but I view it as relatively inexpensive insurance that you hopefully will never need.


• self-draining pouch

• strobe light

• LED flashlight

• automatic PFD light

• pyrotechnic flares

• floating rescue streamer

• chemical glow sticks

• whistle

• signal mirror

• manual horn or small air horn

• dye marker


• throw ropes

• deployable ladder

• line with knots (aid MOB in reboarding)

• throwable devices with lines, such as Lifesling or a horseshoe buoy

• rescue stick or personal retriever

• automatic MOB floating light or strobe

Frank Kehr is a technical writer for Soundings.

This article originally appeared in the March 2009 issue.