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Selective. Unlike traditional VHF, DSC lets you address specific boats privately by entering MMSI numbers or sending your message to all radios in range. If you receive a call, your DSC will ring like a phone and the unit's screen will tell you the identity of the caller.

Calling. Only identification and text-message data are sent digitally. Once two parties make contact, they agree to move to a specific frequency to conduct the call. At this point, many new DSC-enabled radios offer voice scrambling so you can talk in private on your chosen channel.

Although the DSC system was designed for use in emergency situations, the Coast Guard also uses it to send out safety broadcasts to warn boaters of weather changes or other local events that could pose a threat. The agency can track boats as well; because most boaters use Loran or GPS, a local watch station can monitor the courses of several vessels after contact has been established.

Moreover, DSC is also alleviating the problem of false distress calls. Since calls automatically include the boat's identity, most hoaxsters are easy to track down. "The identifying code of the transmitter used in a hoax call would be an extremely powerful piece of evidence in identifying and prosecuting violators," says Richard Smith, chief of the Field Operations Bureau of the U.S. House of Representatives Subcommittee on Coast Guard and Navigation.

To see how DSC actually works at your helm, let's get back to Datamarine's SEA 157. It comes with a numeric keypad and a backlit LCD that displays text, numbers, and 17 icons. To send an emergency call, simply press the red "Distress" key, and the unit instantly transmits a DSC message with your critical data to the nearest watch station.

In addition to DSC capability, the 157 also comes loaded with SEA's  Digital Signal Processing (DSP) software, which controls all radio functions from squelch to noise filtering. Other features include NOAA weather alerts, 10 programmable channels, and lat/lon display, if connected to a Loran or GPS. The unit is also compatible with the MariTel network, the DSC-based national telecommunications system that allows you to send voice, fax, or e-mail messages through its network of coastal and satellite relays. (MariTel received all nine FCC maritime VHF licenses last year, giving it full communications coverage of all navigable U.S. waterways.) The SEA 157 retails for about $749.

Among Raytheon's DSC-enabled radios is the 53 VHF, which comes with similar features, including scan, memory scan, and an oversize LCD for easy reading. The manufacturer's suggested list price is $299.

Simrad offers its RD 68 DSC VHF and RT 1400. Features for the RT 1400 include 54 international channels, 10 private channels, and a programmable directory of MMSI numbers that can be edited any time. It lists for $745. The RD 68 is Simrad's lower-priced version, which provides the same DSC capabilities but fewer features and retails for about $420.

Furuno's latest DSC radio is the FM8500 VHF Transceiver, which is preprogrammed with all major international channels, 10 weather channels, and multiple scanning capabilities. It retails for $1,995.

In the world of marine communications, DSC technology is picking up successfully where cellphones (which are unreliable and have limited range) and satcom systems (which are undeveloped and expensive) have left off. The radios provide both a dependable emergency messaging system and private radio conversations that are more like phone calls. Furthermore, considering the sky-high costs of other emerging communications technology, the price is right.

And, in the end, if a VHF radio with DSC technology helps you with your boating R&R, that's AOK.  

Datamarine Phone: (425) 771-2182. Fax: (425) 771-2650. www.sea-dmi.com.

Furuno Phone: (360) 834-9300. Fax: (360) 833-5199. www.furuno.com.

MariTel Phone: (212) 532-9300. Fax: (212) 532-2677. www.maritelusa.com.

Raytheon Phone: (603) 881-5200. Fax: (603) 864-4756. www.raymarine.com.

Simrad Phone: (954) 922-7700. Fax: (954) 922-0707. www.simrad.com.

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