Rescue 21: The Button That Will Save Your Life

The Coast Guard's new Rescue 21 system brings 911 to the seas.

If you’ve seen a new VHF/DSC radio recently, you may have noticed there’s a little red button. It can save your life. Lift the cover, press the button for five seconds and your radio will tell the Coast Guard’s Rescue 21 VHF communication system and every vessel in radio range that’s equipped with a digital selective calling (DSC) radio that you need assistance. It will also tell who you are, where you are and the reason for your distress call. Your radio will automatically repeat the Mayday until it receives a DSC response from the Coast Guard. You will then hear the Coast Guard calling your vessel on channel 16. With every local DSC radio aware of your distress call and your precise position, it’s very possible that someone may come to your assistance even before the Coast Guard arrives. Consider it the first 911 service for the seas and the most significant improvement in coastal search and rescue since radio.

The urgent need for the system was brought painfully into focus by an incident that happened off Charleston, S. C., on December 29, 1997. Morning Dew, a 34-foot sailboat crewed by the owner, his two teenage sons and a nephew crashed into a jetty at the harbor mouth in Charleston at around 2 a.m. All four drowned, with hypothermia a contributing cause. For various reasons spelled out in the accident report, the Coast Guard did not respond adequately to Morning Dew’s Mayday radio call because of faulty communications. The problems lay both in the use of the vessel’s radio equipment and in the 1970’s-era Coast Guard monitoring system.

At the time, the Rescue 21 system was in its early stages of development, but the Morning Dew incident focused intense interest on the flaws of the aging Coast Guard communication system and the benefits of replacing it. The new Rescue 21 system got the green light. Originally estimated to cost about $300 million, it is now expected to cost about $710 million, with $101 million allocated for 2006.


The system was developed by General Dynamics and evolved from work done by the U.S. and other countries in developing the Global Maritime Distress Signaling System (GMDSS) and its use of the VHF/DSC system to send digital distress hailing calls. Typically, personnel who man the Coast Guard’s existing VHF communication system listen to a number of radios tuned to channel 16, the international hailing and distress frequency, alert for a Mayday call among all of the routine traffic. Rescue 21 improves the channel 16 monitoring system by providing new radios and new antennas and instant high-quality voice playback. In addition, automatic direction finders at each antenna site enable the system’s computers to automatically plot the most probable position of any calling station. It can also record Mayday calls sent with DSC hailing (the red button on your radio) and automatically plot bearings to both DSC and voice calls on channel 16 and other working channels.

I was at the official inauguration of Rescue 21 for the Eastern Shore (stations at Atlantic City, N.J., and Chincoteague, Va.) last December and got to see how it works.

Two computer screens at the operator’s station display a chart of the station’s coverage area and a data screen that is used to control the radios at all of the antenna sites. Multiple radio receivers monitor channel 70, the DSC hailing channel, and channel 16, the voice distress and hailing channel. A DSC Mayday call will cause a “distressed vessel icon to appear at the vessel’s precise position on the chart screen and a data display shows the vessel’s MMSI (maritime mobile service identity number), latitude and longitude on the data screen. In less time than it takes you to read these words the Coast Guard will know that a vessel needs assistance, where it is and, from its MMSI, all of the logged data about the vessel. The Mayday message may also state the number of people on board and the reason for the distress call.


The Rescue 21 system is designed to receive signals from a handheld radio out to 20 nautical miles from shore. The positions of distress calls from boats that don’t have DSC capable radios can be determined by triangulating the automatic direction finder bearings from all of the antennas receiving the signal. The on-screen display shows the most probable search area for the calling vessel.

All of the radio calls made to or from a Rescue 21 station are digitally recorded, with instantaneous playback available to resolve any confusion about the content of the call. Off-line signal processing can be used to further clarify signals garbled by interference or from improper use of the microphone at the vessel’s radio.

Rescue 21’s ability to quickly and accurately fix a vessel’s position based on its distress call will reduce the time spent searching. The system’s direction finding also helps eliminate hoax Mayday calls, since such calls mostly originate from land or very near the shoreline. Hit the red button by accident in your garage and you may be greeted by an angry law enforcement officer.


The benefits of the system go beyond safety. DSC makes contacting another boat on VHF as simple as making a phone call (see Better than a Cell Phone, following story) and provides a new way for yachts to communicate.

Though only the two shoreside stations, Atlantic City and Chincoteague, are currently online, the approximately 655 Coast Guard vessels that normally operate within the 20 nautical mile coastal area covered by Rescue 21 are being equipped with new VHF/DSC radios. In some cases, they may also have UHF radios to communicate with the Coast Guard’s fixed wing aircraft.

Three classes of vessels, ranging from 225- foot buoy tenders to the 18-foot cutter boats that operate from the 87-foot coastal patrol boats will have DSC. The larger boats, including the 87-foot CPBs, 47-foot motor lifeboats and the 41-foot utillity boat will each have 4 VHF/DSC radios, plus the UHF set.


Equipping these vessels with DSC capability will enable the shore stations to see their precise positions on the system chart plotter by transmitting a DSC position request message, thus ensuring that the most appropriate resource is dispatched on each search and rescue mission and will provide a back-up for the shore-based radios. Eventually, a total of more than 1,000 vessels will be fitted with the latest DSC radios.

The Rescue 21 system proved its ability to save lives even before its formal acceptance by the Coast Guard. After Hurricane Katrina destroyed a Coast Guard communications station, a mobile Rescue 21 station was sent to New Orleans where it was used to re-establish radio communications.

A further demonstration of the value of Rescue 21 and its automatic direction finding capability occurred November 15, 2005, when a channel 16 Mayday call was received at the Chincoteague, Va., Rescue 21 station from a sinking fishing boat in the vicinity of Ocean City, Md. The vessel’s position was determined by Rescue 21’s direction-finding system to be some three miles from its reported position. The correct position information made it possible for Coast Guard rescuers to arrive in time to remove three men from the cold water before hypothermia set in.

Though at present only the two East Coast stations are up and running, by this spring Rescue 21 stations will be installed at St. Petersburg, Fla., and Mobile, Ala., providing coverage for a substantial area of the Gulf of Mexico. Stations at Seattle and Port Angeles, Wash., will become operational later in 2006. Fourteen additional stations are scheduled for completion in 2007. For a schedule of installation of the stations check the Coast Guard Website at