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                                                                   EXHIBIT 3.1

 
                          CERTIFICATE OF INCORPORATION
                        OF APPLIED DIGITAL ACCESS, INC.,
                             A DELAWARE CORPORATION
 
     The undersigned, a natural person (the "Sole Incorporator"), for the
purpose of organizing a corporation to conduct the business and promote the
purposes hereinafter stated, under the provisions and subject to the
requirements of the laws of the State of Delaware hereby certifies that:
 
                                   ARTICLE I
 
     The name of this corporation is Applied Digital Access, Inc.
 
                                   ARTICLE II
 
     The address of this corporation's registered office in the State of
Delaware is 30 Old Rudnick Lane, City of Dover, County of Kent 19901. The name
of its registered agent at such address is CorpAmerica, Inc.
 
                                  ARTICLE III
 
     The purpose of this corporation is to engage in any lawful act or activity
for which a corporation may now or hereafter be organized under the Delaware
General Corporation Law.
 
                                   ARTICLE IV
 
     (A)  Classes of Stock. This corporation is authorized to issue two classes
of stock, denominated Common Stock and Preferred Stock. The Common Stock shall
have a par value of $0.001 per share and the Preferred Stock shall have a par
value of $0.001 per share. The total number of shares of Common Stock which the
Corporation is authorized to issue is thirty million (30,000,000), and the total
number of shares of Preferred Stock which the Corporation is authorized to issue
is seven million five hundred thousand (7,500,000), which shares of Preferred
Stock shall be undesignated as to series.
 
     (B)  Issuance of Preferred Stock. The Preferred Stock may be issued from
time to time in one or more series. The Board of Directors is hereby authorized,
by filing one or more certificates pursuant to the Delaware General Corporation
Law (each, a "Preferred Stock Designation"), to fix or alter from time to time
the designations, powers, preferences and rights of each such series of
Preferred Stock and the qualifications, limitations or restrictions thereof,
including without limitation the dividend rights, dividend rate, conversion
rights, voting rights, rights and terms of redemption (including sinking fund
provisions), redemption price or prices, and the liquidation preferences of any
wholly-unissued series of Preferred Stock, and to establish from time to time
the number of shares constituting any such series and the designation thereof,
or any of them; and to increase or decrease the number of shares of any series
subsequent to the issuance of shares of that series, but not below the number of
shares of such series then outstanding. In case the number of shares of any
series shall be decreased in accordance with the foregoing sentence, the shares
constituting such decrease shall resume the status that they had prior to the
adoption of the resolution originally fixing the number of shares of such
series.
 
     (C)  Rights, Preferences, Privileges and Restrictions of Common Stock.
 
     1. Dividend Rights. Subject to the prior or equal rights of holders of all
classes of stock at the time outstanding having prior or equal rights as to
dividends, the holders of the Common Stock shall be entitled to receive, when
and as declared by the Board of Directors, out of any assets of the corporation
legally available therefor, such dividends as may be declared from time to time
by the Board of Directors.
 
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     2. Redemption. The Common Stock is not redeemable upon demand of any holder
thereof or upon demand of this corporation.
 
     3. Voting Rights. The holder of each share of Common Stock shall have the
right to one vote, and shall be entitled to notice of any stockholders' meeting
in accordance with the Bylaws of this corporation, and shall be entitled to vote
upon such matters and in such manner as may be provided by law.
 
                                   ARTICLE V
 
     (A)  Exculpation. A director of the corporation shall not be personally
liable to the corporation or its stockholders for monetary damages for breach of
fiduciary duty as a director, except for liability (i) for any breach of the
director's duty of loyalty to the corporation or its stockholders, (ii) for acts
or omissions not in good faith or which involve intentional misconduct or a
knowing violation of law, (iii) under Section 174 of the Delaware General
Corporation Law or (iv) for any transaction from which the director derived any
improper personal benefit. If the Delaware General Corporation Law is hereafter
amended to further reduce or to authorize, with the approval of the
corporation's stockholders, further reductions in the liability of the
corporation's directors for breach of fiduciary duty, then a director of the
corporation shall not be liable for any such breach to the fullest extent
permitted by the Delaware General Corporation Law as so amended.
 
     (B)  Indemnification. To the extent permitted by applicable law, this
corporation is also authorized to provide indemnification of (and advancement of
expenses to) such agents (and any other persons to which Delaware law permits
this corporation to provide indemnification) through bylaw provisions,
agreements with such agents or other persons, vote of stockholders or
disinterested directors or otherwise, in excess of the indemnification and
advancement otherwise permitted by Section 145 of the Delaware General
Corporation Law, subject only to limits created by applicable Delaware law
(statutory or non-statutory), with respect to actions for breach of duty to the
corporation, its stockholders, and others.
 
     (C)  Effect of Repeal or Modification. Any repeal or modification of any of
the foregoing provisions of this Article V shall be prospective and shall not
adversely affect any right or protection of a director, officer, agent or other
person existing at the time of, or increase the liability of any director of the
corporation with respect to any acts or omissions of such director occurring
prior to, such repeal or modification.
 
                                   ARTICLE VI
 
     Elections of directors need not be by written ballot except and to the
extent provided in the Bylaws of the corporation. The number of directors shall
be as specified in the Bylaws of the corporation. In no event will the number of
directors be less than three. Directors need not be stockholders.
 
                                  ARTICLE VII
 
     Newly created directorships resulting from any increase in the authorized
number of directors shall, unless the Board of Directors determines by
resolution that any such newly created directorship shall be filled by the
stockholders, be filled only by the affirmative vote of a majority of the
directors then in office, even though less than a quorum of the Board of
Directors. Any director elected in accordance with the preceding sentence shall
hold office until such director's successor shall have been elected and
qualified.
 
                                  ARTICLE VIII
 
     No holder of shares of stock of the corporation shall have any preemptive
or other right, except as such rights are expressly provided by contract, to
purchase or subscribe for or receive any shares of any class, or series thereof,
of stock of the corporation, whether now or hereafter authorized, or any
warrants, options, bonds, debentures or other securities convertible into,
exchangeable for or carrying any right to purchase any share of any class, or
series thereof, of stock; but such additional shares of stock and such warrants,
options, bonds, debentures or other securities convertible into, exchangeable
for or carrying any right to purchase any
 
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shares of any class, or series thereof, of stock may be issued or disposed of by
the Board of Directors to such persons, and on such terms and for such lawful
consideration as in its discretion it shall deem advisable or as the corporation
shall have by contract agreed.
 
                                   ARTICLE IX
 
     The corporation is to have a perpetual existence.
 
                                   ARTICLE X
 
     The corporation reserves the right to repeal, alter, amend or rescind any
provision contained in this Certificate of Incorporation and/or any provision
contained in any amendment to or restatement of this Certificate of
Incorporation, in the manner now or hereafter prescribed by statute, and all
rights conferred on stockholders herein are granted subject to this reservation.
 
                                   ARTICLE XI
 
     The Board of Directors may from time to time make, amend, supplement or
repeal the Bylaws by the requisite affirmative vote of directors as set forth in
the Bylaws; provided, however, that the stockholders may change or repeal any
bylaw adopted by the Board of Directors by the requisite affirmative vote of
stockholders as set forth in the Bylaws; and, provided further, that no
amendment or supplement to the Bylaws adopted by the Board of Directors shall
vary or conflict with any amendment or supplement thus adopted by the
stockholders.
 
                                  ARTICLE XII
 
     No action shall be taken by the stockholders of the corporation except at
an annual or special meeting of stockholders called in accordance with the
Bylaws, and no action shall be taken by the stockholders by written consent.
 
                                  ARTICLE XIII
 
     Advance notice of stockholder nominations for the election of directors and
of business to be brought by stockholders before any meeting of the stockholders
of the corporation shall be given in the manner provided in the Bylaws of the
corporation.
 
                                  ARTICLE XIV
 
     The name and the mailing address of the Sole Incorporator is as follows:
 


       Name                                 Mailing Address
- -------------------        --------------------------------------------------
                        
Ross L. Burningham         Brobeck, Phleger & Harrison LLP
                           550 West "C" Street, Suite 1300
                           San Diego, CA 92101

 

 
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     IN WITNESS WHEREOF, this Certificate of Incorporation has been signed this
9th day of June, 1997 by the undersigned who affirms that the statements made
herein are true and correct.

                                          /s/ Ross L. Burningham 
                                          --------------------------------------
                                          Ross L. Burningham, Sole Incorporator
                [SIGNATURE PAGE TO CERTIFICATE OF INCORPORATION
                        OF APPLIED DIGITAL ACCESS, INC.]