Table of Contents:

Definition and Overview

1. Introduction

2. Why Fax Testing Is Necessary

3. Fax Operation Overview

4. Basic Fax System Structure and Process

5. Message Repetitions and Time-Outs

6. Fax System Test Issues

7. Network Test Issues

8. Common Deviations from ITU Standards

9. Fax Testing Customer Types

10. Fax Testing Application Areas

11. Conclusion

Self-Test

Glossary

PDF of this tutorial

Facsimile (fax) technology, the transmission of images over a telephone line, made its appearance in a commercial application about 70 years ago in the form known as wirephoto, which was used to transmit photographs for publication in newspapers. In the early 1960s, the development of modem technology, coupled with the Carterfone Decision, made facsimile machines practical, although the slow transmission time impeded widespread use. However, in the early 1970s, image data compression was introduced, which drastically reduced transmission time and enabled the fax machine to become an integral part of the business environment. Since then, fax machines have become accepted as indispensable communications devices throughout the world, and today there are over 100 million fax machines worldwide. Per year, fax traffic now exceeds 400 billion pages, and the worldwide fax phone bill is more than 91 billion dollars. In fact, fax transmissions account for between 30 and 40 percent of the typical corporate phone bill today.

With the explosive growth of the Internet and the development of techniques for incorporating voice and fax transmission into this new communications world and for bridging the gap between fax and e-mail, the proliferation of fax can be expected to continue and even accelerate.

Because fax machines are so easy to use (put the paper in the hopper, dial the number, and push the send button), many people assume that the whole process is very simple and that testing is not a big issue. The truth of the matter is that communications compatibility between fax devices is a major problem for several reasons:

• Fax technology continues to evolve, with new features being added on a regular basis, and new fax devices must be compatible not only with the latest models but also with the existing installed base of fax machines—some of which date back at least 15 years.
• Many different companies with many different design approaches make fax products, and these products all must communicate with each other.
• Communications technologies and network structures are changing at a rapid pace (the Internet and cellular phone networks in particular), and all of these must be able to handle fax traffic as well as voice.