POWER OF ATTORNEY
KNOW ALL MEN BY THESE PRESENTS, that the undersigned constitutes and appoints Thomas R. Stanton and James E.
Matthews, and each of them, his true and lawful attorneys-in-fact and agents, with full power of substitution, for him and in his
name, place and stead, in any and all capacities, to sign the Annual Report on Form 10-K of ADTRAN, Inc. for the fiscal year
ended December 31, 2006 and any and all amendments thereto, and other documents in connection therewith and to file the
same, with all exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission and
the Nasdaq Stock Market, Inc., granting unto said attorneys-in-fact and agents, and each of them, full power and authority to
do and perform each and every act and thing requisite or necessary to be done, as fully to all intents and purposes as he might
or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his
substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
This 23th day of February 2007.
/s/ Mark C. Smith
Mark C. Smith
Chairman of the Board
/s/ W. Frank Blount
W. Frank Blount
/s/ H. Fenwick Huss
H. Fenwick Huss
/s/ William L. Marks
William L. Marks
/s/ Roy J. Nichols
Roy J. Nichols