Graphic courtesy of General Dynamics
To the Rescue
Digital selective calling and the U.S. Coast Guard Rescue 21 system
By Andy Sumberg
Digital selective calling may change the way you use your marine radio to call for emergency assistance.
DSC offers boaters an array of technology upgrades for marine communications and is designed to work with Rescue 21, the new U.S. Coast Guard command, control and communications system.
According to the Rescue 21 project website, when the system is fully implemented, it will become “the Coast Guard’s primary system to receive distress calls from boats and ships, and perform command, control and communications in the inland and coastal zones for all Coast Guard mission areas.”
The $730 million project was created to address command and control needs identified in a 1995 study recommending significant updates for the existing National Distress and Response System. Between 1995 and 2002, studies and pilot projects resulted in advanced system specifications. Rescue 21 now provides the following capabilities:
Direction finding New towers and antennas facilitate rapid triangulation, giving Coast Guard watch standers the position of an originating radio call in real time. In a minimum-coverage area where triangulation isn’t possible, a line of position to the caller dramatically reduces the search area for Coast Guard crews and improves your chances of a speedy rescue.
Improved interoperability Much has been said about how first responders were unable to communicate with each other on 9/11. Rescue 21 enables first responders and federal, state and local law enforcement agencies to communicate in real time during a crisis.
Simultaneous channel monitoring New equipment expands the number of channels watch standers can monitor from one to six, virtually ensuring your call will get through.
Digital playback and recording of calls Digital archiving with enhanced playback capability allows watch standers to enhance and replay garbled distress calls, dramatically reducing lost calls.
Reduced coverage gaps Accomplished by increased antenna strength, better antenna placement and, in some cases, more towers, the elimination of 88 known coverage gaps throughout the coastal U.S. improves your chances of being heard.
Hoax call identification Rescue 21’s direction-finding capability allows the Coast Guard to identify hoax calls emanating from inland areas. According to Rescue 21 spokeswoman Judy Silverstein, this also helps watch standers prioritize calls, efficiently plan for real emergencies and necessary rescues, and ensure resources are efficiently allocated to real cases. The Coast Guard spends nearly $2 million annually on hoax calls.
Use of portable towers During an emergency, a tower may be obliterated as was the case after Hurricane Katrina in 2005.
“The Disaster Recovery System allows us to resume communications quickly following a natural or manmade disaster,” Silverstein said.
The DRS allows for recovery of Command, Control, and Communication (C3) capability in the aftermath of mud slides, ice storms, hurricanes and tornadoes.
Digital selective calling While Rescue 21 and DSC enhance Coast Guard command and control capabilities, DSC is the part most visible to boaters. While conceived for emergency use, DSC also has a number of important non-emergency uses.
DSC technology allows you to use your marine radio more like a telephone. Your radio conversations will not be private, but you will be able to call one or more specific vessels if you all have properly configured DSC marine radios. You can also place an automated emergency call to the Coast Guard by pressing one button. A properly configured DSC system has three components: a DSC-capable radio, an MMSI number and a two-wire connection to your GPS.
DSC marine radios meet one of three class standards: Class A, International Class D and Class SC-101 (also called U.S. Class D). Class A is the most expensive, starting at about $800. The dual-tuner radio can receive a DSC call whether the operator is transmitting, receiving or in standby mode when the radio is on. Class A radios are now required on commercial vessels.
International Class D radios also have dual tuners but will not receive a DSC call when transmitting. If receiving or on standby mode, the radio can receive a DSC call. Class D’s are much less expensive, starting at around $200.
Class SC-101 radios have a single transmitter and will only receive a DSC call in standby mode, not while transmitting or receiving. An SC-101 can be purchased for as little as $130.
MMSI stands for Maritime Mobile Service Identity. This nine-digit number, similar to a phone number, uniquely identifies you. When you apply for an MMSI number, you provide contact information about the registered owner, emergency contact information and vessel identity information such as the length, color and make of your boat. This information is maintained in a registry that the Coast Guard can access when you place an emergency call.
Enter your MMSI number into the radio by following the instructions in the radio owner’s manual. One note of caution: Most commercially available models only allow you to program your user (station) MMSI twice. If you exceed that number, you will have to send the unit back to the factory for a reset. After you enter the MMSI number, double-check it for accuracy before pressing the “enter” button.
Connecting a GPS to the DSC radio completes the installation. This two-wire NMEA connection uses the most common GPS data exchange format. Once again, your GPS and DSC radio owner’s manuals will explain how to do this.
Now that you’ve properly configured your DSC system, you can hail other boats or the Coast Guard for emergency or non-emergency purposes. The DSC hailing signal is a 0.3-second digital message, transmitted on channel 70, which is reserved solely for these digital transmissions. DSC-equipped radios won’t allow voice calls on channel 70 because they’re illegal according to FCC regulations.
Non-emergency DSC calling While DSC functions of various radios may differ, I have run into three types of DSC calls: individual, group and all ships. Individual and group calls can be made to boats within receiving range as long as their MMSI numbers have been saved in the directory of your DSC radio. When you enter someone’s MMSI, you also include a name so the radio’s directory shows a list of recognizable names, not just a series of nine-digit numbers.
To make an individual or group call, set the radio to the desired channel. Select the individual or group members from the radio’s directory and then press the “send” button. A digital hailing signal is sent on Channel 70. DSC radios will ignore the signal unless their MMSI is included. When a designated radio receives the message, it will emit an auditory signal, display the calling MMSI (and the name of the calling boat if listed in the receiving radio) and switch to the chosen working channel for regular radio conversation.
An all-ships call works the same way, except any DSC radio in range will receive the call and, under normal circumstances, switch to the designated working channel. Individual boat owners can disable the automatic channel switching function. On many radios, it’s also possible to assign the call a topic—emergency, safety or routine—so the operator receiving the DSC hail can determine the nature of the call.
Emergency DSC calling DSC radios have a button, usually covered by a red plastic door, labeled “distress.” Do not test this button! The operator makes an emergency call by pressing this button for five seconds. This emergency distress call may be heard by any DSC-equipped radio, including boaters with DSC radios, Coast Guard boats and planes, and eventually Coast Guard ground stations. Any receiving DSC radio display will indicate an emergency, show the latitude/longitude position of the calling boat and automatically switch the receiving radio to channel 16. Rescue 21-implemented Coast Guard ground stations will digitally acknowledge the call and force the calling DSC radio to channel 16 to initiate a conversation.
If you receive a distress call, listen for Coast Guard acknowledgement on channel 16. If you don’t hear an acknowledgement after two minutes, call the Coast Guard and inform them of the distress call. Your radio will automatically store the MMSI and latitude/longitude of the calling vessel as well as the time of the emergency call. You should also determine your distance from the vessel in distress, as you may be able to provide assistance.
Other DSC features Most DSC radios have the ability to request the position of another DSC-equipped boat. You can set up your radio to automatically provide this information or to ask you whether you want to transmit this information every time a request is received. Many radios allow emergency calls to be assigned a “subject” such as abandoning ship, capsizing, collision, disabled, explosion, fire, flooding, grounding, listing, man overboard, piracy and sinking. These designations allow for voiceless data transmission in an emergency.
Rescue 21 implementation Rescue 21 is currently being implemented in stages throughout the nation. When it’s fully implemented, Coast Guard boats and aircraft should have DSC radios. While these radios don’t have the same capabilities as the Coast Guard Operations Centers, they will operate much like the high-end, commercially available (Class A) DSC radios.
To date, Rescue 21 stands the watch along 2,200 miles of coastline. The system has been implemented in Atlantic City, N.J.; the Eastern Shore (Virginia, Maryland and Delaware); Mobile, Ala.; St. Petersburg, Fla.; Seattle and Port Angeles, Wash.; and in a portion of New Orleans. Approximately 36 more installations are scheduled.
Until Rescue 21 is operational in your area, both non-emergency and emergency DSC calls can still be initiated. Other boats with DSC radios (including Coast Guard vessels) will be able to receive calls. To communicate directly with a Coast Guard ground station, it’s best to initiate a call the old-fashioned way—hailing by voice on channel 16.
The major advantage of DSC is its ability to send an automatic and prolonged mayday call in the event of an emergency. Therefore, a properly installed DSC is crucial.
Lt/C Andy Sumberg, AP, is currently SEO of Charles River Sail & Power Squadron and commodore of the Catalina 350 International Association. Raised in Miami and currently living near Boston, he has been boating most of his life. Having worked in the computer industry, he has followed closely how technology has changed boating over recent years. He currently sails with his wife, Mindy, out of Westport, Mass.