1There are many established PBX vendors. Why is ADTRAN entering the PBX market? ADTRAN® has a 19-year successful history in the telecom market dating back to our original products that helped public telephone companies upgrade to high speed digital services worldwide. Today, we produce more than 1,300 products for both carrier and enterprise markets, and one of our competencies is the ability to design and engineer lower cost, integrated solutions. Our most recent enterprise successes are in the

. . . . . . . data terminal ready FCC. . . . . . . . . Federal Communications Commission GUI. . . . . . . . . graphical user interface IRQ. . . . . . . . . interrupt request ISDN. . . . . . . . Integrated Services Digital Network ISP. . . . . . . . . . Internet Service Provider 61203153L2-20 Express 3000 User Manual Appendix E. Acronyms and Abbreviations kbps. . . . . . . . kilobits per second LCD . . . . . . . . liquid crystal display LDN. . . . . . . . local directory number LED . . . . . . .