Report of Independent Registered Public Accounting Firm To Board of Directors and Stockholders of ADTRAN, Inc.:  PricewaterhouseCoopers LLP Birmingham, Alabama February 27, 2014 ADTRAN 2013 Annual Report 34 A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (i) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (ii) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and  that receipts and expenditures of the company are being made only in accordance with authorizations of management and  directors of the company; and (iii) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements. Because  of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections  of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of  changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate. In our opinion, the consolidated financial statements listed in the accompanying index present fairly, in all material respects,  the financial position of ADTRAN, Inc. and its subsidiaries at December 31, 2013 and December 31, 2012 and the results of  their operations and their cash flows for each of the three years in the period ended December 31, 2013 in conformity with  accounting principles generally accepted in the United States of America. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2013, based on criteria established in  Internal Control—Integrated Framework (1992)  issued by the Committee of Sponsoring Organizations of the Treadway  Commission (COSO). The Company’s management is responsible for these financial statements, for maintaining effective  internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting,  included in the accompanying  Management’s Report On Internal Control Over Financial Reporting . Our responsibility is to express opinions on these financial statements, and on the Company’s internal control over financial reporting based on our integrated audits. We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audits to obtain reasonable assurance  about whether the financial statements are free of material misstatement and whether effective internal control over financial  reporting was maintained in all material respects. Our audits of the financial statements included examining, on a test basis,  evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and  significant estimates made by management, and evaluating the overall financial statement presentation. Our audit of internal  control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control  based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the  circumstances. We believe that our audits provide a reasonable basis for our opinions.