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Hilton Head fires up cellular data network.

Fire departments seldom test emerging communication technologies. But under the leadership of Chief David A. MacLellan, the Sea Pines Forest Beach Fire Department (SPFD) on Hilton Head, S.C., already has more than a year's experience using a cellular network to transmit data.

SPFD combined Norwood, Mass.-based Microcom's cellular modem technology with a Novell NetWare LAN (local area network), allowing firefighters to access information such as building design and the location of hazardous materials. In addition, the interface helps SPFD improve fire fighting as well as making communications from fire engines to the central firehouse more secure.

SPFD began examining cellular data connectivity two years ago. "Cellular data transmission offered many advantages compared to other radio transmission mechanisms," notes Robert Manis, network administrator at SPFD.

Mobile radio voice transmissions are susceptible to eavesdropping. "A lot of people spend time monitoring fire department calls," explains Manis. "There are instances when a firefighter does not want sensitive information broadcast to the public." Manis figured a cellular data connection could eliminate the problem.

A second limitation of mobile radio was an inability to access the SPFD's computers. SPFD regularly inspects local buildings, collects information about structure, function and contents, and generates reports for local, state and federal agencies. Such information, if readily accessible at a fire scene, enhances firefighters, understanding of the fire site.

Historically, the process was paper-intensive. In 1988, the department purchased application software from SunPro Fire Services, Sunnyside, Wash., to automate the recordkeeping. SPFD runs the software on a LAN with 17 IBM-compatible PCs at the central fire station. A second SPFD firehouse with a handful of PCs uses dial-up connections to access the LAN.

"By examining a building's structure, a firefighter can decide the simplest way to keep the fire from spreading and determine if special precautions are needed to battle items such as hazardous waste materials," he says.

So Manis set out in search of products that could support cellular data connections. "Initially, I expected that more products would be available," he says.

"The island is relatively small and does not need a large of number of cell sites. Still, there are areas where getting a connection is difficult. Products without MNP (Microcom Networking Protocol) 10 were unable to overcome this problem and provide us with reliable cellular data communications," Manis says.

Manis did find a few products to test. For the tests, the fire department added an IBM PS/2 computer to its central command van. The van, housed at the central fire station, arrives at every fire and acts as a clearinghouse for all department communications. Firefighters communicate with many agencies, such as the police and Coast Guard.

At the end of 1991, SPFD evaluated Microcom's Cellular Data Link (CDL) 300, a V.22bis modem housed in a Mitsubishi Series 1500 transportable cellular phone. The CDL 300 supports both voice and data connections and includes a "turbo mode" feature that pushes modulation to either 3.2K or 4K.

The CDL 300 modem is equipped with MNP 10, which includes four functions, known as Adverse Channel Enhancements (ACE), that regulate modulation and packet size, optimizing transmission reliability and performance.

Data transmissions over cellular networks are affected by the variable quality of the cellular radio frequency signal. This is due to distance from the radio tower (cell), electrostatic interference, structural interference and crosstalk. Because radio signal propagation is so variable, the transmit level must be adjusted constantly. The cellular service does this by momentarily interrupting voice transmissions, sending transmit adjust-level information, and then continuing the voice call, a process known as "blank and burst."

For voice users, this is the annoying pause that occurs frequently. For data users, however, blank and burst can terminate the call because non-MNP 10 modems can interpret this interruption as loss of the modem carrier signal.

Back at the firehouse, on the other side of the connection, a Gateway 2000 PC acts as a communications server. The device is equipped with a C96 MNP 10 modem so firefighters can converse with the central firehouse PCs.

SPFD would like one enhancement: Higher communications speeds. "You always want to transmit information faster because it will be cheaper," Manis says. "Currently, the CDL 300 operates at 4.8 kb/s, but we are interested in a version that works at 9.6 kb/s."

"Cellular line costs have fallen during the past 18 months, but they are still high," notes Manis. "In some cases, our firefighters are on-line to the central station office for two to three hours, so we can run up some significant telephone bills."

Despite the high cost, the use of the cellular connection is expected to increase because of fire department consolidation. Previously, two departments served Hilton Head Island. The two merged in July, expanding the number of fire stations to seven. Manis says the CDL 300-equipped communications van will remain an integral part of the department's fire-fighting resources.

"Cellular technology may not be as simple to use as land line dial-up connections, but it offers unique features not available with a regular phone," concludes Manis.
COPYRIGHT 1993 Nelson Publishing
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Copyright 1993 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Sea Pines Forest Beach Fire Department
Publication:Communications News
Date:Oct 1, 1993
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