Printer Friendly

Two-Way Radio Goes Digital.

Ten years ago the big news in two-way radio was "digital". RCA introduced its Voice-PLUS Digital communications equipment line for two-way mobile systems combining normal voice transmissions with the ab ility to send up to 99 digital code messages instantly by push button, with automatic vehicle identification, a digital data master station, and a selective-calling sender. Motorola introduced its "MODAT" data system which allowed automatic transfer of information between vehicles and the dispatch center. Using the Modat control head, the vehicle operator pressed the desired function button and the message and vehicle ID were automatically sent. The mobile unit automatically sent its message only when the frequency was clear. It automatically retransmitted when the channel was clear until acknowledgement was received, or a maximum of four times. When the message had been sent, received and decoded at the base station, an "acknowledge" message was transmitted to the mobile unit, causing the "acknowledge" light to go out. A total of 24 digital messages could be incorporated into one equipped mobile unit.

Today, a decade later, the future of mobile digital communications looks bright . . . with organizations like Federal Express "going digital" in a big way.

While earlier mobile data terminals were not very user-friendly . . . and while the early radios lacked reliability and the early computers used in the systems lacked flexibility . . . today the technology, says Business Radio, is "enhanced, refined and field-proven" and mobile digital radio is again on the move. The systems available today are greatly improved.

Mobile Data International, a Canadian company that designs and manufactures exclusively mobile digital systems, is enjoying a surge in systems sales in North America and in offshore markets as well. Since 1978, MDI has installed systems for public safety organizations in North America, Europe, and the Far East. The Phoenix, Arizona Fire Department's communications system, considered the world's most advanced, includes MDI terminals. Police in Stockton, California and Vancouver, Canada use MDI terminals to run nationwide license checks in under ten seconds, and these forces will soon be joined by police in Calgary, New York, Toronto, and Oakland, California.

More recently, MDI's market has broadened from its public-safety base. A major Toronto power utility uses MDI terminals to improve safety and cost-efficiency. A Calgary taxi fleet operator uses MDTs to eliminate favoritism by dispatchers. Federal Express uses them to improve efficiency and morale. A major manufacturer of household chemical products has ordered an MDI system that will become an integral part of its warehousing and materials handling systems.

"All indications are," says Business Radio, "that mobile digital technology will become an important part of the business radio scene in the coming years."

An excellent article in the February, 1984 issue of Business Radio describes the MDI systems which feature compact, rugged, self-contained terminals that are microprocessor-based and user-friendly, saying: "A typical MDI system consists of a dispatch station with keyboard and video screen, a host computer, channel control equipment, a base station, and mobile terminals with screens and keyboards that replace mikes and speakers. Indicators on the MDT screen advise the operator of its operating status. Messages composed on a keyboard, or canned messages stored in the system's memory (status messages, for example) are transmitted with a touch of a key.

"One advantage of the system is speed. MDI'S SYSTEM TRANSMITS AT 4800 BPS . . . meaning that a complete message is normally transmitted, received, and made available to be read in less than three seconds. Because of this speed, and the nature of the coded message, eavesdropping is virtually impossible. Also, depending on the way the system is configured, the dispatcher can choose to send any message to a single unit, to a group of units, or to all units.

"Channel efficiency is another reason some fleet operators go to digital technology. MDI's system can put up to 300 mobile units on one full-duplex channel with its largest, most sophisticated MDT (315-character CRT display, six-screen memory). With the Model 7031 terminal (two-line liquid crystal display and 12-line memory) the system can handle up to 700 units on one channel. Given the difficulty of acquiring additional frequencies and the desirability of having all units on one channel, this is a powerful argument for digital communication.

"A third advantage the mobile data communications system has is that the system can guarantee that every message is received with perfect accuracy. MDI's system will not display a message that contains even a single-character error; its error correction software delivers the message intact. Conditions at the vehicle . . . noise or confusion . . . do not affect the driver's comprehension of the dispatch. If he is away from the vehicle, the message is stored until he returns. The terminal can store up to six messages, which, in the case of some terminals (like the MDI Model 9031 MDT) can include graphics like maps, for example, or diagrams.

"In addition to these basic benefits, there are all the possibilities that go along with data processing. The terminal is an extension of a computer system. Through it, field operators can access the organization's data base to get information without bothering the dispatcher. Blank forms (credit card checks for taxi drivers, work orders for utility trucks) can be stored in the system and called up with a single keystroke. In the case of police organizations, patrol officers can access county, state, and federal data banks, unaided, from their vehicles. Consider the efficiencies inherent in a mobile radio system that records all activity and allows it to be printed out at the end of the shift, eliminating handwritten reports and forms. System software can include management reports of activity drawn from the computer record. Fixed terminals at headquarters can access the computer anytime for supervisory reasons without troubling the dispatcher. Apart from dispatching, the system can be used for electronic mail; messages can be sent from any fixed or mobile terminals to any other terminal."

Federal Express started looking into digital communication in 1977, when it had become apparent that the company's two-way voice system wasn't keeping up with the growing demand. Channel congestion was bad, especially during the critical late afternoon peak traffic periods. Federal Express began looking at mobile digital radio as a possible solution. Fed Ex engineers identified some specific system requirements . . . like shared data/voice channels and voice priority for handling emergencies and exceptions . . . and MDI agreed to rewrite its software to accommodate the company's special needs. A ten-van test was staged at company headquarters in Memphis. This was followed by an installation in which half the Chicago fleet (65 vehicles) were equipped with MDTs.

In the Federal Express system, customers phone into regional call centers, where the pickup requests are entered into central computers and dispatched over leased lines to city stations. There they are displayed on terminal screens for the dispatchers, who transmit them to the vans. They are stored in the MDT's six-screen memory; the driver presses a button to scroll through the memory. When drivers report for a shift, they turn on their MDTs, call up a form on the screen, and sign on. The computer in the local office transmits all the dispatches assigned to each route. Drivers can organize their day immediately. They can also call up on the CRT the standard forms that list the dispatches assigned to their routes, or that allow them to change status or request a retransmission. As they work their way through their routes, they advise the dispatcher of their progress by pressing status buttons on the MDT. A flashing dot on the screen alerts the driver when the MDT has received an additional dispatch during the afternoon.

The MDT system offers several important benefits for Federal Express and its drivers. Management and dispatchers can see what's going on at a glance, adjusting route size and work load anytime. Dispatchers now send out dispatches as soon as they get them, rather than tending to wait because of heavy channel traffic, and drivers are less likely to get last-minute panic pickup calls. Message errors do not occur. Morale is better because drivers have better control of their time and are better able to plan. At the end of the day, they know that they have not left any customer waiting, and they have not missed a single message.

The unit is compact and rugged, and maintenance technicians can remove it for maintenance with the turn of a single key. There are no additional boxes or cables.

As a result of its Chicago test, Federal Express has installed MDT systems in New York and Los Angeles. In New York, the company found that the system allowed them to reduce the number of vans on the streets while improving service. Over a period during which its New York business doubled, the number of dispatchers . . . two . . . stayed the same. Federal Express is now installing MDTs nationwide, and late this year expects to have equipped 50 offices and 5,000 vans with MDI equipment!

The Phoenix, arizona Fire Department's $5.2 million communications system is considered by many to be the world's best, the Phoenix uses mobile data terminals to display both text and graphics for emergency use. When the dispatcher decides which station and which vehicles are to receive his message, the system automatically transmits it to CRTs and printers in the stations, and to MDTs in the vehicles. When the men reach their vehicles, the information is waiting for them.

John Simmons, fire/computer services administrator, calls the Phoenix Fire Department's $5.2 million computer-aided dispatch system "the most advanced in the world," and says this is the first time mobile data terminals have been used to dispatch fire fighting equipment. "The system," says Simmons, "features 12 custom dispatch consoles, each housing two 15-inch, high-resolution color CRT terminals. Each dispatch console has a 20-channel radio control system which is microprocessor controlled and and fully redundant. The graphics capabilities of the system are used for charts, graphs, maps and building plans . . . with color print out available. The CAD system is composed of 134 different programs consisting of a total of approximately 500,000 separate instructions. These programs are supported by 57 data files containing approximately 187 million characters of information. In an average 24-hour period, the system will transmit and receive a total of 130,000 messages."

Using about 250 microprocessors, all interacting with each other, the system incorporates 225 fixed and mobile digital CRT terminals on-line 24-hours a day, seven days a week.

The system is designed for 200 fire and EMS vehicles, 12 dispatch consoles, 20 remote administrative CRT terminals and 65 fire station terminals and printers. Simmons reports that, "Presently the system is operating with 47 stations, 148 MDTs 10 administrative sites and 100,000 dispatches annually."

The promise that was mobile digital communications a decade ago is being fulfilled today.
COPYRIGHT 1984 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1984 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Publication:Communications News
Date:Sep 1, 1984
Previous Article:Facsimile Fulfills Its Promise.
Next Article:Cable Television Comes of Age.

Related Articles
Use microwave, fiber to build new network.
Local radio joins the digital age.
Local radio to move into the digital age; Up to 10 new stations on way.
Just plug it in.
To beep or not to beep, that is the question.

Terms of use | Copyright © 2016 Farlex, Inc. | Feedback | For webmasters