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                                                                    EXHIBIT 3.16


                                     BY-LAWS

                                       OF

                            PLEXUS ENTERPRISES, INC.

                                    ARTICLE I

                                     OFFICES

      Section 1. Registered Office. The registered office of the Corporation
shall be in the City of Wilmington, County of New Castle, State of Delaware.

      Section 2. Other Offices. The principal office of the Corporation outside
the State of Delaware shall be in the City of San Antonio, State of Texas. The
Corporation may also have offices at such other places both within and without
the State of Delaware as the Board of Directors may from time to time determine
or the business of the Corporation may require.


                                   ARTICLE II

                            MEETINGS OF STOCKHOLDERS

      Section 1. Time and Place of Meeting. All meetings of the stockholders
shall be held at such time and at such place within or without the State of
Delaware as shall be determined by the Board of Directors.

      Section 2. Annual Meetings. Annual meetings of the stockholders shall be
held on the first Wednesday in May each year, if not a legal holiday, and if a
legal holiday, then on the next full business day following, at 10:00 a.m., at
which the stockholders shall elect by a plurality vote a board of directors and
transact such other business as may properly be brought before the meeting.

      Section 3. Special Meetings. Special meetings of the stockholders, for any
proper purpose or purposes, unless otherwise prescribed by statute or by the
Certificate of Incorporation of the Corporation, may be called at any time by
the President or the Board of Directors, and shall be called by the President or
Secretary at the request in writing of the holders of shares of the Corporation
then issued, outstanding and entitled to vote at the meeting which represent not
less than 25% of the votes entitled to be cast at the meeting. Such request
shall state the purpose or
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purposes of the proposed meeting. Business transacted at special meetings shall
be confined to the purpose or purposes stated in the notice of the meeting.

      Section 4. Notice. Written or printed notice stating the place, date and
hour of any meeting of stockholders, and in the case of a special meeting, the
purpose or purposes for which the meeting is called, shall be delivered not less
than ten (10) nor more than sixty (6O) days before the date of the meeting,
either personally or by mail, by or at the direction of the President, a Vice
President, the Secretary, an Assistant Secretary or the person calling the
meeting, to each stockholder of record entitled to vote at such meeting. If
mailed, such notice shall be deemed to be delivered when deposited in the United
States mail, postage prepaid, addressed to the stockholder at his address as it
appears on the stock ledger of the Corporation.

      Section 5. List of Shareholders. The officer or agent of the Corporation
having charge of the stock ledger of the Corporation shall make, at least ten
(10) days before each meeting of the stockholders, a complete list of the
stockholders entitled to vote at such meeting or any adjournment thereof,
arranged in alphabetical order, and showing the address of each stockholder and
the number of shares registered in the name of each stockholder. Such list, for
a period of ten (10) days prior to such meeting, shall be open to the
examination of any stockholder, for any purpose germane to the meeting, during
ordinary business hours, either at a place within the city where the meeting is
to be held, which place shall be specified in the notice of the meeting or, if
not so specified, at the place where the meeting is to be held. Such list shall
also be produced and kept open at the time and place of the meeting and shall be
subject to the inspection of any stockholder during the whole time of the
meeting. The stock ledger shall be the only evidence as to who are the
stockholders entitled to examine such list or stock ledger, or to vote at any
meetings of stockholders.

      Section 6. Quorum. The holders of issued and outstanding shares which
represent not less than a majority of the votes entitled to be cast thereat,
present in person or represented by proxy, shall constitute a quorum at all
meetings of the stockholders for the transaction of business except as otherwise
provided by statute or by the Certificate of Incorporation (all references to
the Certificate of Incorporation in these By-Laws includes any Certificate of
Designation respecting a resolution of the Board of Directors providing for the
issue of a series of preferred stock of the Corporation and which has been filed
in the office of the Secretary of State of the State of Delaware). If, however,
such quorum shall not be present or represented at any meeting of the
stockholders, a majority in interest of the stockholders entitled to vote
thereat, present in person or represented by proxy, shall have power to adjourn
the meeting from time to time until a quorum shall be present or represented
without notice of the adjourned meeting other than announcement of the time and
place thereof at the meeting at which the adjournment is taken. When any
adjourned meeting is reconvened and a quorum shall be present or represented,
any business may be transacted which might have been transacted at the original
meeting. If the adjournment is for more than thirty (3O) days, or if after the
adjournment a new record


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date is fixed for the adjourned meeting, a notice of the adjourned meeting shall
be given to each stockholder of record entitled to vote at the meeting.

      Section 7. Voting. When a quorum is present at any meeting, the vote of
the holders of a majority of the shares present or represented by proxy at such
meeting and entitled to vote shall decide any question brought before such
meeting, unless the vote of a different number is expressly required by statute,
the Certificate of Incorporation or these By-Laws. The voting for election of
directors may be by written ballot or other means.

      Section 8. Proxy. Unless otherwise provided in the Certificate of
Incorporation, each stockholder shall at every meeting of the stockholders be
entitled to one vote in person or by proxy for each share having voting power
held by such stockholder. Every proxy must be executed in writing (which shall
include telegraphing or cabling) by the stockholder or by his duly authorized
attorney-in-fact, but no proxy shall be voted on after three years from its
date, unless the proxy provides for a longer period.

      Section 9. Action Without a Meeting. Unless otherwise provided in the
Certificate of Incorporation, any action required to be taken at any annual or
special meeting of stockholders of the Corporation, or any action which may be
taken at any annual or special meeting of such stockholders, may be taken
without a meeting, without prior notice and without a vote, if a consent in
writing, setting forth the action so taken, shall be signed by the holders of
outstanding shares of the Corporation having not less than the minimum number of
votes that would be necessary to authorize or take such action at a meeting at
which all shares entitled to vote thereon were present and voted. Prompt notice
of the taking of the corporate action without a meeting by less than unanimous
written consent shall be given to those stockholders who have not consented in
writing.

                                   ARTICLE III

                                    DIRECTORS

      Section 1. Number of Directors. The number of directors of the Corporation
shall be three (3). Directors shall be elected at the annual meeting of the
stockholders, except as provided in Section 2 of this Article, and each director
shall hold office until his successor is elected and qualified. Directors need
not be stockholders of the Corporation.

      Section 2. Vacancies and Additional Directorships. Unless otherwise
provided in the Certificate of Incorporation, vacancies and newly created
directorships resulting from any increase in the authorized number of directors
may be filled by a majority of the directors then in office, though less than a
quorum, or by a sole remaining director, and the directors so chosen shall hold
office until the next annual election and until their successors are duly
elected and shall qualify.


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      Section 3. General Powers. The business of the Corporation shall be
managed by its Board of Directors, which may exercise all powers of the
Corporation and do all such lawful acts and things as are not by statute, or by
the Certificate of Incorporation or by these By-Laws directed or required to be
exercised or done by the stockholders.

      Section 4. Place of Meetings. The directors of the Corporation may hold
their meetings, both regular and special, either within or without the State
of Delaware.

      Section 5. Annual Meetings. The first meeting of each newly elected Board
of Directors shall be held without further notice immediately following the
annual meeting of the stockholders, and at the same place, unless by unanimous
consent of the directors then elected and serving such time or place shall be
changed.

      Section 6. Regular Meetings. Regular meetings of the Board of Directors
may be held without notice at such time and place as shall from time to time
be determined by the Board of Directors.

      Section 7. Special Meetings. Special meetings of the Board of Directors
may be called by either the Chairman of the Board or the President on two
business days' notice to each director, either personally or by mail or by
telegram, and in the case of notice by mail, such notice shall be deemed to have
been given on the third day following the date on which such notice is deposited
in the United States mail, postage prepaid, properly addressed to such director.
Special meetings shall be called by the President or Secretary in like manner
and on like notice on the written request of any two directors.

      Section 8. Quorum. At all meetings of the Board of Directors the presence
of a majority of the number of directors constituting the whole Board shall be
necessary and sufficient to constitute a quorum for the transaction of business,
and the affirmative vote of at least a majority of the directors present at any
meeting at which there is a quorum shall be the act of the Board of Directors,
except as may be otherwise specifically provided by statute, by the Certificate
of Incorporation or by these By-Laws. If a quorum shall not be present at any
meeting of directors, the directors present thereat may adjourn the meeting from
time to time without notice other than announcement at the meeting, until a
quorum shall be present.

      Section 9. Committees. The Board of Directors may, by resolution passed by
a majority of the whole Board, designate one or more committees in addition to
the executive committee provided for in Section 10 of this Article III, each
committee to consist of one or more of the directors of the Corporation. Any
such committee, to the extent provided in the resolution of the Board of
Directors, shall have and may exercise all the powers and authority of the Board
of Directors in the management of the business and affairs of the Corporation,
and may authorize the seal of the Corporation to be affixed to all papers which
may require it; but no such committee shall have the


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power or authority in reference to amending the Certificate of Incorporation,
adopting an agreement of merger or consolidation, recommending to the
stockholders the sale, lease or exchange of all or substantially all of the
Corporation's property and assets, recommending to the stockholders a
dissolution of the Corporation or a revocation of a dissolution, or amending the
By-Laws of the Corporation; and, unless the resolution or the Certificate of
Incorporation expressly so provide, no such committee shall have the power or
authority to declare a dividend or to authorize the issuance of stock or to
adopt a certificate of ownership and merger. Such committee or committees shall
have such name or names as may be determined from time to time by resolution
adopted by the Board of Directors. Each committee shall keep regular minutes of
its meetings and report the same to the Board of Directors when required.

      Section 10. Executive Committee. The Board of Directors may, by resolution
passed by a majority of the whole Board, designate an executive committee which
shall consist of two or more members. The Chairman of the Board and the
President shall be members of the executive committee. The executive committee
shall have, except as otherwise provided by law or by resolution of the Board of
Directors, all the authority of the Board of Directors during the intervals
between the meetings of the Board of Directors.

      Section 11. Compensation of Directors. Directors, as such, shall not
receive any stated salary for their services, but, by resolution of the Board of
Directors, a fixed sum and expenses of attendance, if any, may be allowed for
attendance at each regular or special meeting of the Board of Directors,
provided that nothing herein contained shall be construed to preclude any
director from serving the Corporation in any other capacity and receiving
compensation therefor. Members of the committees of the Board of Directors may,
by resolution of the Board of Directors, be allowed like compensation for
attending meetings of such committees.

      Section 12. Action Without a Meeting. Unless otherwise restricted by the
Certificate of Incorporation or these By-Laws, any action required or permitted
to be taken at any meeting of the Board of Directors or of any committee
designated by the Board of Directors may be taken without a meeting if all
members of the Board or committee, as the case may be, consent thereto in
writing, and the writing or writings are filed with the minutes of proceedings
of the Board or Committee.

      Section 13. Meetings by Conference Call, Etc. Unless otherwise restricted
by the Certificate of Incorporation or these By-Laws, members of the Board of
Directors, or any committee designated by the Board of Directors, may
participate in a meeting of the Board of Directors, or any committee, by means
of conference telephone or similar communications equipment by means of which
all persons participating in the meeting can hear each other, and such
participation in a meeting shall constitute presence in person at the meeting.


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      Section 14. Removal of Directors. Unless otherwise restricted by the
Certificate of Incorporation or by law, any director or the entire Board of
Directors may be removed, with or without cause, by the holders of a majority of
shares entitled to vote at an election of directors.

      Section 15. Reliance Upon Books. Directors and members of any committee
designated by the Board of Directors shall, in the performance of their duties,
be fully protected in relying in good faith upon the books of accounts or
reports made to the Corporation by any of its officers, or by an independent
certified public accountant, or by an appraiser selected with reasonable care by
the Board of Directors or by any such committee, or in relying in good faith
upon other records of the Corporation.

                                   ARTICLE IV

                                     NOTICES

      Section 1. Form of Notice. Whenever under the provisions of the statutes,
the Certificate of Incorporation or these By-Laws, notice is required to be
given to any director or stockholder, and no provision is made as to how such
notice shall be given, it shall not be construed to mean personal notice, but
any such notice may be given in writing, by mail, postage prepaid, addressed to
such director or stockholder at such address as appears on the books of the
Corporation. Any notice required or permitted to be given by mail shall be
deemed to be given at the time when the same be thus deposited in the United
States mail as aforesaid.

      Section 2. Waiver. Whenever any notice is required to be given to any
director or stockholder of the Corporation under the provisions of the statutes,
the Certificate of Incorporation or these By-Laws, a waiver thereof in writing
signed by the person or persons entitled to such notice, whether before or after
the time stated in such notice, shall be deemed equivalent to the giving of such
notice. Neither the business to be transacted at, nor the purpose of, any
regular or special meeting of the stockholders, directors, or members of a
committee of directors need be specified in any written waiver of notice.
Attendance of a person at a meeting shall constitute a waiver of notice of such
meeting, except when the attendance is for the express purpose of objecting, at
the beginning of the meeting, to the transaction of any business because the
meeting is not lawfully called or convened.

                                    ARTICLE V

                                    OFFICERS

      Section 1. In General. The officers of the Corporation shall be elected by
the Board of Directors and shall be a President, a Vice President, a Secretary
and a Treasurer. The Board of Directors may also, if it chooses to do so, elect
a Chairman of the Board, additional Vice Presidents, one or more Assistant
Secretaries and one or 


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more Assistant Treasurers, all of whom shall also be officers. Two or more
offices may be held by the same person, unless the Certificate of Incorporation
or these By-Laws otherwise provide.

      Section 2. Election. The Board of Directors at its first meeting after
each annual meeting of the stockholders shall elect a President, who shall be a
member of the Board, and shall elect one or more vice presidents, a secretary
and a treasurer who need not be members of the Board. The Board of Directors
also may appoint a Chairman of the Board, who shall be a member of the Board,
and such other officers and agents as it shall deem necessary and may determine
the salaries of all officers and agents from time to time. The officers shall
hold office until their successors are chosen and qualified. Any officer elected
or appointed by the Board of Directors may be removed, for or without cause, at
any time by a majority vote of the whole Board. Election or appointment of an
officer or agent shall not of itself create contract rights.

      Section 3. Chairman of the Board. The Chairman of the Board, if there be
one, shall preside at all meetings of the stockholders and of the Board of
Directors, and shall be responsible for developing the general over-all policies
and programs of the Corporation and shall have such other powers and duties as
may be assigned to or vested in him from time to time by the Board of Directors.

      Section 4. President. The President shall have general responsibility for
carrying out the business and affairs of the Corporation, and shall have general
supervision and direction of all other officers of the Corporation, except the
Chairman of the Board, if there be one. In the absence of the Chairman of the
Board or if a Chairman of the Board has not been elected, he shall preside at
all meetings of the stockholders and of the Board of Directors. The President
shall have such other powers and duties as may be assigned to or vested in him
from time to time by the Board of Directors.

      Section 5. Vice Presidents. The Vice President or, if there be more than
one, the Vice Presidents in the order of their seniority or in any other order
determined by the Board of Directors, shall, in the absence or disability of the
Chairman of the Board, if there be one, or the President, perform the duties and
exercise the powers of such offices, respectively, and shall generally assist
the Chairman of the Board, if there be one, and President and perform such other
duties as the Board of Directors shall prescribe.

      Section 6. Secretary. The Secretary shall attend all meetings of the Board
of Directors and all meetings of the stockholders and record all votes and the
minutes of all proceedings in a book to be kept for that purpose, and shall
perform like duties for committees of the Board when required. He shall give, or
cause to be given, notice of all meetings of the stockholders and special
meetings of the Board of Directors, and shall perform such other duties as may
be prescribed by the Board of Directors or President, under whose supervision he
shall be. He shall keep in safe custody the seal


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of the Corporation and he, or an assistant secretary, shall have authority to
affix the same to any instrument requiring it and when so affixed it may be
attested by his signature or by the signature of such assistant secretary. The
Board of Directors may give general authority to any other officer to affix the
seal of the Corporation and to attest the affixing by his signature.

      Section 7. Assistant Secretaries. Any Assistant Secretary shall, in the
absence or disability of the Secretary, perform the duties and exercise the
powers of the Secretary and shall perform such other duties as may be prescribed
by the Board of Directors or the President.

      Section 8. Treasurer. The Treasurer shall have the custody of all
corporate funds and securities, and shall keep full and accurate accounts of
receipts and disbursements of the Corporation, and shall deposit all moneys and
other valuable effects in the name and to the credit of the Corporation in such
depositories as may be designated by the Board of Directors. He shall disburse
the funds of the Corporation in such manner as may be authorized by the Board of
Directors from time to time, making proper vouchers for such disbursements, and
shall render to the President and directors, at the regular meetings of the
Board or whenever they may require it, an account of all his transactions as
Treasurer and of the financial condition of the Corporation, and shall perform
such other duties as may be prescribed by the Board of Directors or the
President.

      Section 9. Assistant Treasurers. Any Assistant Treasurer shall, in the
absence or disability of the Treasurer, perform the duties and exercise the
powers of the Treasurer and shall perform such other duties as may be prescribed
by the Board of Directors or the President.

      Section 10. Bonding. If required by the Board of Directors, all or certain
of the officers shall give the Corporation a bond in such form, in such sum and
with such surety or sureties as shall be satisfactory to the Board, for the
faithful performance of the duties of their office and for the restoration to
the Corporation, in case of their death, resignation, retirement or removal from
office, of all books, papers, vouchers, money and other property of whatever
kind in their possession or under their control belonging to the Corporation.


                                   ARTICLE VI

                        CERTIFICATES REPRESENTING SHARES

      Section 1. Form of certificates. The Corporation shall deliver
certificates representing all shares to which stockholders are entitled.
Certificates representing shares of the Corporation shall be in such form as
shall be determined by the Board of Directors and shall be numbered
consecutively and entered in the books of the


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Corporation as they are issued. Each certificate shall state on the face thereof
the holder's name, the number, class of shares, and the par value of the shares
or a statement that the shares are without par value. They shall be signed by
the Chairman of the Board of Directors, or the President or a Vice President,
and by the Secretary or an Assistant Secretary, or the Treasurer or an Assistant
Treasurer, and may be sealed with the seal of the Corporation or a facsimile
thereof if the Corporation shall then have a seal. If any certificate is
countersigned by a transfer agent or registered by a registrar, either of which
is other than the Corporation or an employee of the Corporation, the signatures
of the Corporation's officers may be facsimiles. In case any officer, transfer
agent or registrar who has signed, or whose facsimile signature has been placed
on such certificate, shall cease to be such officer, transfer agent or
registrar, whether because of death, resignation or otherwise, before such
certificate has been delivered by the Corporation or its agents, such
certificate may nevertheless be issued and delivered with the same effect as if
he were such officer, transfer agent or registrar at the date of issue.

      If the corporation shall be authorized to issue more than one class of
stock or more than one series of any class, the powers, designations,
preferences and relative, participating, optional or other special rights of
each class of stock or series thereof and the qualification, limitations or
restrictions or such preferences and/or rights shall be set forth in full or
summarized on the face or back of the certificate which the Corporation shall
issue to represent such class or series of stock, provided that, except as
otherwise provided in section 202 of the General Corporation Law of Delaware, in
lieu of the foregoing requirements, there may be set forth on the face or back
of the certificate which the Corporation shall issue to represent such class or
series of stock, a statement that the Corporation will furnish without charge to
each stockholder who so requests the powers, designations, preferences and
relative, participating, optional or other special rights of each class of stock
or series thereof and the qualifications, limitations or restrictions of such
preferences and/or rights.

      Section 2. Lost Certificates. The Board of Directors may direct that a new
certificate be issued in place of any certificate theretofore issued by the
Corporation alleged to have been lost, stolen or destroyed, upon the making of
an affidavit of that fact by the person claiming the certificate to be lost,
stolen or destroyed. When authorizing the issue of a new certificate, the Board
of Directors, in its discretion and as a condition precedent to the issuance
thereof, may require the owner of the lost, stolen or destroyed certificate, or
his legal representative, to advertise the same in such manner as it shall
require and/or give the Corporation a bond in such form, in such sum, and with
such surety or sureties as it may direct as indemnity against any claim that may
be made against the Corporation with respect to the certificate alleged to have
been lost, stolen or destroyed.

      Section 3. Transfer of Shares. Shares of stock shall be transferable only
on the books of the Corporation by the holder thereof in person or by his duly
authorized attorney and, upon surrender to the Corporation or to the transfer
agent of the


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Corporation of a certificate representing shares duly endorsed or accompanied by
proper evidence of succession, assignment or authority to transfer, it shall be
the duty of the Corporation or the transfer agent of the Corporation to issue a
new certificate to the person entitled thereto, cancel the old certificate and
record the transaction upon its books.

      Section 4. Registered Stockholders. The Corporation shall be entitled to
recognize the holder of record of any share or shares of stock as the holder in
fact thereof and, accordingly, shall not be bound to recognize any equitable or
other claim to or interest in such share or shares on the part of any other
person, whether or not it shall have express or other notice thereof, except as
otherwise provided by law.

      Section 5. Record Date. In order that the Corporation may determine the
stockholders entitled to notice of or to vote at any meeting of stockholders or
any adjournment thereof, or to express consent to corporate action in writing
without a meeting, or entitled to receive payment of any dividend or other
distribution or allotment of any rights, or entitled to exercise any rights in
respect of any change, conversion or exchange of stock or for the purpose of any
other lawful action, the Board of Directors may fix, in advance, a record date,
which shall not be more than sixty nor less than ten days before the date of
such meeting, nor more than sixty days prior to any other action. A
determination of stockholders of record entitled to notice of or to vote at a
meeting of stockholders shall apply to any adjournment of the meeting; provided,
however, that the Board of Directors may fix a new record date for the adjourned
meeting.


                                   ARTICLE VII

                               GENERAL PROVISIONS

      Section 1. Dividends. Dividends upon the outstanding shares of the
Corporation, subject to the provisions of the statutes and of the Certificate of
Incorporation, if any, may be declared by the Board of Directors at any regular
or special meeting. Dividends may be declared and paid in cash, in property, or
in shares of the Corporation, provided that all such declarations and payments
of dividends shall be in strict compliance with all applicable laws and the
Certificate of Incorporation.

      Section 2. Fiscal Year. The fiscal year of the Corporation shall be as
fixed by the Board of Directors.

      Section 3. Seal. The corporate seal may be used by causing it or a
facsimile thereof to be impressed or affixed or reproduced or otherwise.

      Section 4. Annual Statement. The Board of Directors shall present at each
annual meeting and when called for by vote of the stockholders at any special
meeting


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of the stockholders, a full and clear statement of the business and
condition of the Corporation.


                                  ARTICLE VIII

                                     BY-LAWS

      Section 1. Amendments. These By-Laws may be altered, amended or repealed
and new By-Laws may be adopted by the stockholders or by the Board of Directors,
when such power is conferred upon the Board of Directors by the Certificate of
Incorporation, at any regular meeting of the stockholders or of the Board of
Directors or at any special meeting of the stockholders or of the Board of
Directors if notice of such alteration, amendment, repeal or adoption of new
By-Laws be contained in the notice of such special meeting. If the power to
adopt, amend or repeal by-laws is conferred upon the Board of Directors by the
Certificate of Incorporation, it shall not divest or limit the power of the
stockholders to adopt, amend or repeal by-laws. Any action of the Board of
Directors to effect any alteration, amendment, repeal or adoption of new By-Laws
may be taken only by the affirmative vote of a majority of the whole Board.

      Section 2. When By-Laws Silent. It is expressly recognized that when
the By-Laws are silent as to the manner of performing any corporate function,
the provisions of the statutes shall control.


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