Printer Friendly

After Years of Steady Growth Use of Facsimile Explodes.

According to Webster, the word facsimile means the transmission and reproduction of graphic matter, an exact copy, by wire or radio. While the description is accurate, it falls far short of describing some of the percentions that exists about the word "facsimile." For those far removed, the word conjures up a picture of a machine taht goes clunk! clunk!, located in a police station surrounded by several people, all waiting for the reception of a photograph or fingerprints to be completed. Still there are other groups that use or have used early facsimile equipment and continue to perceive the process as slow, smelly and cumbersome. The fact is, in today's marketplace, just the opposite is true.

To those of us in the business, the term facsimile describes the rapid transmission of text, graphics and handwritten information over ordinary telephone lines.

Advancements in technology have made possible thermal printing with no detectable odor. Applications of digital technology and improved quality of phone lines provide the capability of sub-minute transmission speeds. A thorough understanding of machine/operator human factors and machine processing have made it possible for today's fax machines to be virtually autoamtic. Moreover, the communications capability provided by facsimile today is way beyond that originally offered in the early days of facsimile.

The beginning of the general office facsimile business si benchmarked by a joint agreement between Magnavox and Xerox Corporation in 1966 to produce and market the Telecopier I, a facsimile machine specifically desgned for the business environment. Since then, many other companies have entered the market elevating the total facsimile terminal population to nearly 350,000 in the United States and Canada, and 800,000 worldwide. This growth over the last 17 years has set the stage for the facsimile explosion that is currently upon us, as new users begin to expand their communications capability with the addition of facsimile equipment.

Existing users are sharing in this growth by upgrading their equipment from older, low-speed analog facsimile devices to new high-speed digital units with high resolution scanning and printing. Facsimile transmissions that took six minutes per page to complete over ordinary telephone lines in 1966 can now be done in less than a minute.

As the number of facsimile manufacturers increased, offering a wide variety of features and capabilities, so did the need for standardization to establish operating compatibility between the different machines. This need for standardization was satisfied by the Recommendations of the International Telegraph and Telephone Consultative Committee (CCITT) for facsimile equipment. In general, facsimile terminals are divided into four categories, dependent on document transmission speeds; low, medium, high and very high. Within each category, communication compatibility between any two machines (from different manufacturers) is made possible by designing the operational aspects of the equipment to satisfy requirements prescribed by the CCITT Recommendations. CCITT, however, does not classify facsimile equipment into categories, but rather, into Groups in accordance with the Recommendations. Table 1 defines the relationship between the four categories and CCITT Groups. Accordingly, a Group 3 machine is digital with sub-one-minute transmission speed. CCITT Agreement for Group 3 Recommendations

In late 1980, CCITT announced agreement of the Group 3 Recommendation for facsimile. This event led the way for numerous manufacturers to announce their new digital facsimile machines. Today, there are more than a dozen companies marketing Group 3 facsimile terminals in both desk-top and console models. to exemplify the many time-saving and unique functions that can be offered by a Group 3 digital facsimile machine, the following capabilities of a representative terminal, the Xerox Telecopier 495, are listed:

* Transmission circuit--ordinary voice grade telephone lines.

* Backward compatibility (option)--CCITT Groups 2 and 1 with automatic send/receive speed identification.

* Diagnostics--test send/receive functions of machine operation.

* Messsage Assurance--monitors transmission to ensure document was received.

* Time, date, terminal ID (option)--prints calendar information on the top of each received copy. Also providing identification codes for polling and transmission terminals.

* Automatic dialer (option)--provides delayed start and automatic dialing to multiple remote terminals.

* Auto receive--receives documents unattended.

* Automatic paper cutter--cuts received copy from roll-fed recording paper.

* Transmission speed--up to 9,600 b/s and 24 seconds per page.

* Digital modem--9,600/7,200/4,800/2,400 b/s with automatic fallback based on line quality.

Of these many features, the capability of the digital modem to adjust to a specific transmission speed according to the line quality of the DDD (direct distance dialing) networks is of particular importance. Specified by CCITT Recommendations V.27, V.29 and T.30, the facsimile terminal controls the modem via a sophisticated speed adjustment algorithm to choose the proper transmission rate for a bit error rate (BER) required for good copy quality while maintaining high throughput speeds.

When a DDD point-to-point connection is established, the facsimile terminal initiating the connection transmits an internally generated digital sequence which is used by the receiver for synchronization. At the receiver, upon detection of the transmitted line energy, the auto gain control (AGC) is adjusted, phase and frequency are locked to the received carrier, bit rate timing is established, equalizers for line amplitude and phase characteristics are chosen and the training sequence is detected. Once this process has been completed, data can be transmitted and received.

The training sequence is a digital sequence of a particular pattern that can be identified at the receiver using a compatible pattern. An algorithm measures the received signal quality and, if necessary, requests the transmitter to reduce the transmission rate. Modem transmission rate training starts at 9,600 b/s and decreases to 7,200, 4,800, 2,400 b/s according to the signal-to-noise ratio and other impairments of the line connection. The selected modem speed is displayed on the Telecopier 495 control panel at the beginning of a transmission. Comparison of Telephone Lines

Using the modem speed information, a study had been undertaken comparing the relative quality of telephone lines between local, national and international connections. The test was structured so that calls were made routinely by casual operators over a four-month period and the automatic selected modem speed was recorded. One hundred calls were made distributively over a local loop exchange, and to cities within the US. Another 100 calls were made internationally to Japan and England.

From this test data, it was found that, in general, the quality of point-to-point connection was predominantly determined by the local exchange and for the most part, independent of distance and AT&T's long-haul lines. Notably, calls nationally showed that 73 percent of the transmissions were at the 9,600 b/s rate, and that 100 percent were at 7,200 b/s or above.

Table 2 shows that the local connections yield only slightly better results than when compared to either the national or international telephone line connections. These results suggest that the fundamental quality of the telephone connections is determined by the connection from the user's location through, and including, the local telephone service's central office. This data leads to the conclusion that AT&T communications network can and does provide high quality lines which can effectively handle 9,600 b/s of data as well as voice communications.

The expectation based upon this information is that, given a good quality local loop line, users of today's highly sophisticated Group 3 facsimile machines can successfully transmit their facsimile traffic at the rate of 9,600 b/s.

Figure 1 shows the cost trends for the total cost per month (including facsimile equipment and long-distance telephone charges) versus the number of pages transmitted per day. It is evident that for long distance calls being billed at daytime DDD rates for facsimile traffic of eight or more pages per day, it is economically beneficial to use a Group 3 facsimile transceiver rather than a Group 2 facsimile transceiver. In the case of Group 1 machines, the break point is about five pages per day. As competition heats up, driving machine costs downward, the cost trend line for Group 3 is also expected to move downward. This is indicated by the predicted cost trend line in Figure 1. The increase in the slope of the line is anticipated as a result of the trend to find system and networking solutions for high volume facsimile traffic incorporating fully featured machines that can be integrated with computers.

Without question, the application of today's high technology to facsimile, including sophisticated adaptive algorithms, data compression schemes, and scanning and printing, have contributed to improved throughput, higher quality, and lower cost for facsimile transactions.

At the 1983 International Communications Association show, Xerox demonstrated the Telecopier 495-1. The company showed how a document may be created on a personal computer (text and graphics), converted electronically to a compatible facsimile format, and then transmitted to facsimile machines worldwide without the need to create and scan the document at the point of origin. By adding an RS-232C port, along with other refinements to the machine, a whole new dimension of the computer world has been opened up to facsimile.

While the initial application of the 495-1/RS-232C port has been demonstrated with a Xerox 820-II personal computer to provide functions such as store and forward, ASCII-to-facsimile conversion, and sequential broadcasting, applications are not restricted to the 820-II.

Figure 2 shows a typical 495-I/820-II serving as a facsimile, text and graphics information distribution hub, providing a communications link over ordinary telephone lines for a network of facsimile machines. This is one of many applications that can now be made with facsimile and computer/message equipment.
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
Author:Perna, I.
Publication:Communications News
Date:Jan 1, 1984
Words:1587
Previous Article:Telpak May Be Dead, but Closer Look Shows a Better Deal Ahead.
Next Article:Northeastern Hospital Delegates Telephone Cost Control to Department Heads with CDR.
Topics:


Related Articles
Facsimile Systems Provide Speed, Accuracy and Economy.
Facsimile Fulfills Its Promise.
Railroad System Employs Faxes That Work All the Livelong Day.
Digital Facsimile Generates Savings Gusher for Oil Firm.
Business is in love with fax: plain paper paces growth.
Auto production driving L. American rubber industry.
Making history.

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