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                                                                     EXHIBIT 3.1
                              
                              AMENDED AND RESTATED

                          CERTIFICATE OF INCORPORATION

                                       OF

                            NICHOLS TXEN CORPORATION


         The undersigned corporation filed its Certificate of Incorporation with
the Delaware Secretary of State on September 17, 1996 under the name Nichols
SELECT Corporation. On November 5, 1997, the corporation filed a Certificate of
Amendment to its Certificate of Incorporation changing its name to "Nichols TXEN
Corporation." These Amended and Restated Articles have been duly adopted by the
board of directors and shareholders of the corporation in accordance with the
provisions of Section 245 & 242 of the General Corporation Law of the State of
Delaware.

         Therefore, in accordance with the General Corporation Law of the State
of Delaware, the undersigned corporation, desiring to amend and restate its
Certificate of Incorporation pursuant to Section 245 & 242 of the General
Corporation Law of the State of Delaware, hereby certifies as follows:
                                   
                                    ARTICLE I

                                      Name
                                     
         The name of the corporation is Nichols TXEN Corporation.

                                   ARTICLE II

                               Period of Duration

         The corporation shall have perpetual existence.

                                   ARTICLE III

                                     Purpose

         The corporation shall have the right to transact any and all lawful
business for which corporations may be organized under the General Corporation
Law of the State of Delaware.

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                                   ARTICLE IV

                                     Capital

         The aggregate number of shares which the corporation is authorized to
issue is Thirty Million (30,000,000) shares of $.01 par value voting common
stock all of the same class and none preferred.

                                    ARTICLE V

                           Registered Agent and Office

         The location and mailing address of the registered office of the
corporation is Corporation Trust Center, 1209 Orange Street in the City of
Wilmington, County of New Castle, Delaware 19801.

         The name of the registered agent of the corporation at such address is
The Corporation Trust Company.
                                   ARTICLE VI

                       Action by Unanimous Written Consent

         Action of the shareholders may be taken by unanimous written consent
without meeting and it shall have the same effect as the unanimous vote of the
shareholders. Action of the directors may be taken by unanimous written consent
without meeting and it shall have the same effect as the unanimous vote of the
directors.
                                   ARTICLE VII

                               Number of Directors

         The board of directors of the corporation shall consist of one or more
members as established by the By-Laws of the corporation.

                                  ARTICLE VIII

                              No Preemptive Rights

         Existing shareholders shall not have preemptive rights with respect to
the issuance of additional shares of stock.


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                                   ARTICLE IX

                                     By-Laws

         The board of directors shall have the power to adopt, amend or repeal
By-Laws of the corporation.

                                    ARTICLE X

                             Limitation of Liability

         A director of the corporation shall not be personally liable to the
corporation or its shareholders for money 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 shareholders, (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 an improper personal
benefit.
                                   ARTICLE XI

                              Indemnity; Insurance

         The corporation shall indemnify any person who was or is a party or is
threatened to be made a party to any threatened, pending or completed action,
suit or proceeding, whether civil, criminal, administrative or investigative by
reason of the fact that he or she is or was serving as a director, officer,
employee, fiduciary or agent of the corporation or is or was serving at the
request of the corporation as a director, officer, employee, fiduciary or agent
of another corporation, partnership, joint venture, trust or other enterprise,
against expenses (including attorney's fees), judgments, fines and amounts paid
in settlement actually and reasonably incurred by him or her in connection with
such action, suit or proceeding to the full extent permitted by the General
Corporation Law of the State of Delaware from time to time in effect. The
indemnification provided by this provision shall not be deemed exclusive of any
other rights to which any such person seeking indemnification may be entitled
under any statute, by-law, agreement, vote of stockholders or disinterested
directors or 


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otherwise, both as to action in his or her official capacity and as to action in
another capacity while holding such office, and shall continue as to a person
who has ceased to be a director, officer, employee or agent and shall inure to
the benefit of the heirs, executors and administrators of such person. The term
"enterprise" shall include, but not be limited to, plans and trusts established
or for the benefit of employees of the corporation, including plans and trusts
governed under the Employee Retirement Income Security Act of 1974, as amended.

         The corporation shall have authority, but shall not be required, to
purchase and maintain insurance on behalf of any person who is or was a
director, officer, employee or agent of the corporation, or is or was serving at
the request of the corporation as a director, officer, employee or agent of
another corporation, partnership, joint venture, trust or other enterprise
against any liability asserted against him and incurred by him in any such
capacity or arising out of his status as such, whether or not the corporation
would have the power to indemnify him against such liability. The corporation
may (but shall not be required to) pay for or reimburse the reasonable expenses
incurred by a person entitled to indemnification who is a party to a proceeding
in advance of the final disposition of the proceeding if: (i) the party
furnishes the corporation with a written affirmation of his or her good-faith
belief that he or she conducted himself or herself in good faith and he or she
reasonably believed that the conduct was in the best interests of the
corporation; (ii) the party furnishes the corporation with a written
undertaking, executed personally or on his or her behalf, to repay the advance
if it is determined that he or she did not meet such standard of conduct; and
(iii) determination is made that the facts then known to those making the
determination would not preclude indemnification under this Article.


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                                  ARTICLE XII

                                   Committees

         The board of directors shall have the power to designate one or more
committees, each committee to consist of one or more of the directors of the
corporation. The Board may designate one or more directors as alternate members
of a committee, who may replace an absent or disqualified member at a meeting of
the committee. The By-Laws may provide that in the absence or disqualification
of a member of a committee, the members thereof present at a meeting and not
disqualified from voting, whether or not they constitute a quorum, may
unanimously appoint another member of the board to act at the meeting, and each
member thereof, shall serve at the pleasure of the board. A committee designated
pursuant to this paragraph, to the extent provided in the resolution of the
board or in the By-Laws, may exercise all powers and authority of the board in
management of the business and affairs of the corporation not prohibited by the
General Corporation Law of the State of Delaware.

         IN WITNESS WHEREOF, the undersigned has executed this Amended and
Restated Certificate of Incorporation as of the 6th day of November, 1998.


                                  Nichols TXEN Corporation




                                  By: /s/          Paul D. Reaves
                                     -----------------------------------------
                                     Paul D. Reaves, Chief Executive Officer


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