EXHIBIT 10.11

THIRD AMENDMENT TO LETTER OF CREDIT AND REIMBURSEMENT AGREEMENT

        This Third Amendment to Letter of Credit and Reimbursement Agreement
(this “Third Amendment”) is made and entered into as of the 15th day of April,
2004, by and between POWELL ELECTRICAL SYSTEMS, INC., a Delaware corporation
(“Borrower”), successor by merger of Delta-Unibus Corp., and BANK OF AMERICA,
N.A., a national banking association (“Lender”).

W I T N E S S E T H:

        WHEREAS, pursuant to that certain Letter of Credit and Reimbursement
Agreement (as heretofore amended, the “Loan Agreement”) dated October 25, 2001,
Lender agreed to make certain loans to Borrower upon the terms and conditions
therein contained; and

        WHEREAS, pursuant to the terms and conditions of a First Amendment to
Letter of Credit and Reimbursement Agreement dated as of January 11, 2002, and a
Second Amendment to Letter of Credit and Reimbursement Agreement dated as of
October 31, 2003, Borrower and Lender modified and amended certain terms and
provisions of the Loan Agreement; and

        WHEREAS, Borrower and Lender desire to further modify and amend certain
terms and provisions of the Loan Agreement.

        NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, Borrower and Lender agree as
follows:

        1.     Amendments to Loan Agreement. Subject to and upon the full and
complete satisfaction of the terms and conditions of numerical Section 3 below,
the Loan Agreement is amended and modified as follows:

        1.1.     All references to Delta-Unibus Corp. in the Loan Agreement, the
Guaranty, and each of the other Related Documents to which Lender is a party are
deleted in their entirety and replaced in each case with a reference to Powell
Electrical Systems, Inc.

        2.     Reaffirmation of Representations and Warranties. To induce the
Lender to enter into this Third Amendment, Borrower hereby reaffirms, as of the
date hereof, its representations and warranties in their entirety contained in
the Loan Agreement and in all other Related Documents executed by Borrower
pursuant thereto (except to the extent such representations and warranties
relate solely to an earlier date in which case they shall have been true and
accurate in all respects as of such earlier date) and additionally represents
and warrants as follows:

        2.1.     The execution and delivery of this Third Amendment and the
performance by Borrower of its obligations under this Third Amendment and the
Loan Agreement as amended hereby are within Borrower’s powers, have been duly
authorized by all necessary action, have received all necessary governmental and
other approvals (if any shall be required), and do not and will not contravene
or conflict with the governance documents of Borrower or any provision of law,
any presently existing requirement or restriction imposed by any judicial,
arbitral, regulatory or governmental instrumentality or constitute a default
under, or result in the creation or imposition of any lien other than a lien
permitted by the terms of the Loan Agreement upon any property or assets of
Borrower or any Guarantor under, any agreement, instrument or indenture by which
Borrower or any Guarantor is bound;

        2.2.     This Third Amendment has been duly executed and delivered on
behalf of Borrower and this Third Amendment and the Loan Agreement, as amended
hereby, are the legal, valid and binding obligations of Borrower, enforceable in
accordance with their terms subject as to enforcement only to bankruptcy,
insolvency, reorganization, moratorium or other similar laws and equitable
principles affecting the enforcement of creditors’ rights generally; and

        2.3.     No Default or Event of Default has occurred and is continuing
after giving effect to this Third Amendment.

        3.     Conditions. The effectiveness of this Third Amendment is subject
to the following conditions, all in form and substance satisfactory to the
Lender:

        3.1.     The Lender shall have received and approved:

          (a)         Third Amendment. A counterpart of this Third Amendment
executed by Borrower and each Guarantor;

          (b)         Bond Documents. Evidence that all approvals,
modifications, and consents under and with respect to the Bank Bonds and the
Reimbursement Agreement to the merger of Delta-Unibus Corp. into Powell
Electrical Manufacturing Company (now known as Borrower) have been received and
executed (as applicable);

          (c)         Other Documents. Such other documents as the Lender may
reasonably request (which shall include without limitation, amendments to the
Letter of Credit and the related Letter of Credit Application, and all
authorization documents required by Lender in connection with the foregoing);
and

          (d)         Expenses. Reimbursement for all of Lender’s fees and
expenses (including attorneys’ fees) incurred in connection with the
preparation, negotiation, and execution of this Third Amendment.

        3.2.     All legal matters incident to the execution and delivery of
this Third Amendment shall be satisfactory to the Lender.

        3.3.     No Default or Event of Default shall be then continuing.

        4.     Assumption. Without limiting the foregoing, Borrower expressly
assumes the obligations of Delta-Unibus Corp. under and with respect to the Loan
Agreement and the Letter of Credit (as modified by this Agreement), and agrees
to be primarily liable and responsible for the performance, observation,
payment, and satisfaction of all obligations, duties, liabilities, and
responsibilities of Delta-Unibus under the Loan Agreement and the Letter of
Credit. Upon the full and complete satisfaction of the conditions listed in
numerical Section 3, Lender hereby consents to the merger of Delta-Unibus Corp.
and Unibus, Inc. into Powell Electrical Manufacturing Company (now known as
Borrower), and the express assumption by Borrower of Delta-Unibus Corp.‘s
obligations under the Loan Agreement and the Letter of Credit. Nothing contained
herein shall constitute an agreement or consent by Lender to any future merger
and future assumptions of such obligations and rights. In consideration of the
foregoing, upon the full and complete satisfaction of the conditions listed in
numerical Section 3, Lender does hereby agree that the Guaranty is modified to
remove Powell Electrical Manufacturing Company and Unibus, Inc. as Guarantors
thereunder.

        5.     Arbitration and Waiver of Jury Trial.

          (a)         THIS SECTION CONCERNS THE RESOLUTION OF ANY CONTROVERSIES
OR CLAIMS BETWEEN THE BORROWER AND THE LENDER, WHETHER ARISING IN CONTRACT, TORT
OR BY STATUTE, INCLUDING BUT NOT LIMITED TO CONTROVERSIES OR CLAIMS THAT ARISE
OUT OF OR RELATE TO: (i) THIS THIRD AMENDMENT AND THE LOAN AGREEMENT (INCLUDING
ANY RENEWALS, EXTENSIONS OR MODIFICATIONS); OR (ii) ANY DOCUMENT RELATED TO THIS
THIRD AMENDMENT AND THE LOAN AGREEMENT (COLLECTIVELY A “CLAIM”).

          (b)         AT THE REQUEST OF THE BORROWER OR LENDER, ANY CLAIM SHALL
BE RESOLVED BY BINDING ARBITRATION IN ACCORDANCE WITH THE FEDERAL ARBITRATION
ACT (TITLE 9, U. S. CODE) (THE “ACT”). THE ACT WILL APPLY EVEN THOUGH THIS
AGREEMENT PROVIDES THAT IT IS GOVERNED BY THE LAW OF A SPECIFIED STATE.

            (c)         ARBITRATION PROCEEDINGS WILL BE DETERMINED IN ACCORDANCE
WITH THE ACT, THE APPLICABLE RULES AND PROCEDURES FOR THE ARBITRATION OF
DISPUTES OF JAMS OR ANY SUCCESSOR THEREOF (“JAMS”), AND THE TERMS OF THIS
SECTION. IN THE EVENT OF ANY INCONSISTENCY, THE TERMS OF THIS PARAGRAPH SHALL
CONTROL.

          (d)         THE ARBITRATION SHALL BE ADMINISTERED BY JAMS AND
CONDUCTED IN ANY U. S. STATE WHERE REAL OR TANGIBLE PERSONAL PROPERTY COLLATERAL
FOR THIS CREDIT IS LOCATED OR IF THERE IS NO SUCH COLLATERAL, IN TEXAS. ALL
CLAIMS SHALL BE DETERMINED BY ONE ARBITRATOR; HOWEVER, IF CLAIMS EXCEED
$5,000,000, UPON THE REQUEST OF ANY PARTY, THE CLAIMS SHALL BE DECIDED BY THREE
ARBITRATORS. ALL ARBITRATION HEARINGS SHALL COMMENCE WITHIN 90 DAYS OF THE
DEMAND FOR ARBITRATION AND CLOSE WITHIN 90 DAYS OF COMMENCEMENT AND THE AWARD OF
THE ARBITRATOR(S) SHALL BE ISSUED WITHIN 30 DAYS OF THE CLOSE OF THE HEARING.
HOWEVER, THE ARBITRATOR(S), UPON A SHOWING OF GOOD CAUSE, MAY EXTEND THE
COMMENCEMENT OF THE HEARING FOR UP TO AN ADDITIONAL 60 DAYS. THE ARBITRATOR(S)
SHALL PROVIDE A CONCISE WRITTEN STATEMENT OF REASONS FOR THE AWARD. THE
ARBITRATION AWARD MAY BE SUBMITTED TO ANY COURT HAVING JURISDICTION TO BE
CONFIRMED AND ENFORCED.

          (e)         THE ARBITRATOR(S) WILL HAVE THE AUTHORITY TO DECIDE
WHETHER ANY CLAIM IS BARRED BY THE STATUTE OF LIMITATIONS AND, IF SO, TO DISMISS
THE ARBITRATION ON THAT BASIS. FOR PURPOSES OF THE APPLICATION OF THE STATUTE OF
LIMITATIONS, THE SERVICE ON JAMS UNDER APPLICABLE JAMS RULES OF A NOTICE OF
CLAIM IS THE EQUIVALENT OF THE FILING OF A LAWSUIT. ANY DISPUTE CONCERNING THIS
ARBITRATION PROVISION OR WHETHER A CLAIM IS ARBITRABLE SHALL BE DETERMINED BY
THE ARBITRATOR(S). THE ARBITRATOR(S) SHALL HAVE THE POWER TO AWARD LEGAL FEES
PURSUANT TO THE TERMS OF THIS THIRD AMENDMENT AND THE LOAN AGREEMENT.

          (f)         THIS SECTION DOES NOT LIMIT THE RIGHT OF THE BORROWER OR
THE LENDER TO: (i) EXERCISE SELF-HELP REMEDIES, SUCH AS BUT NOT LIMITED TO,
SETOFF; (ii) INITIATE JUDICIAL OR NONJUDICIAL FORECLOSURE AGAINST ANY REAL OR
PERSONAL PROPERTY COLLATERAL; (iii) EXERCISE ANY JUDICIAL OR POWER OF SALE
RIGHTS, OR (iv) ACT IN A COURT OF LAW TO OBTAIN AN INTERIM REMEDY, SUCH AS BUT
NOT LIMITED TO, INJUNCTIVE RELIEF, WRIT OF POSSESSION OR APPOINTMENT OF A
RECEIVER, OR ADDITIONAL OR SUPPLEMENTARY REMEDIES.

          (g)         BY AGREEING TO BINDING ARBITRATION, THE PARTIES
IRREVOCABLY AND VOLUNTARILY WAIVE ANY RIGHT THEY MAY HAVE TO A TRIAL BY JURY IN
RESPECT OF ANY CLAIM. FURTHERMORE, WITHOUT INTENDING IN ANY WAY TO LIMIT THIS
AGREEMENT TO ARBITRATE, TO THE EXTENT ANY CLAIM IS NOT ARBITRATED, THE PARTIES
IRREVOCABLY AND VOLUNTARILY WAIVE ANY RIGHT THEY MAY HAVE TO A TRIAL BY JURY IN
RESPECT OF SUCH CLAIM. THIS PROVISION IS A MATERIAL INDUCEMENT FOR THE PARTIES
ENTERING INTO THIS THIRD AMENDMENT.

        6.     NO CONTROL BY LENDER. BORROWER AGREES AND ACKNOWLEDGES THAT ALL
OF THE COVENANTS AND AGREEMENTS PROVIDED FOR AND MADE BY BORROWER IN THIS THIRD
AMENDMENT, THE LOAN AGREEMENT, AND IN THE OTHER LOAN DOCUMENTS ARE THE RESULT OF
EXTENSIVE AND ARMS-LENGTH NEGOTIATIONS BETWEEN BORROWER AND LENDER. LENDER’S
RIGHTS AND REMEDIES PROVIDED FOR IN THE LOAN AGREEMENT AND IN THE OTHER LOAN
DOCUMENTS ARE INTENDED TO PROVIDE LENDER WITH A RIGHT TO OVERSEE BORROWER’S
ACTIVITIES AS THEY RELATE TO THE LOAN TRANSACTIONS PROVIDED FOR IN THE LOAN
AGREEMENT, WHICH RIGHT IS BASED ON LENDER’S VESTED INTEREST IN BORROWER’S
ABILITY TO PAY THE NOTES AND PERFORM THE OTHER OBLIGATIONS. NONE OF THE
COVENANTS OR OTHER PROVISIONS CONTAINED IN THE LOAN AGREEMENT SHALL, OR SHALL BE
DEEMED TO, GIVE LENDER THE RIGHT OR POWER TO EXERCISE CONTROL OVER, OR OTHERWISE
IMPAIR, THE DAY-TO-DAY AFFAIRS, OPERATIONS, AND MANAGEMENT OF BORROWER; PROVIDED
THAT IF LENDER BECOMES THE OWNER OF ANY STOCK OF ANY ENTITY, WHICH ENTITY OWNS
AN INTEREST IN BORROWER, WHETHER THROUGH FORECLOSURE OR OTHERWISE, LENDER
THEREAFTER SHALL BE ENTITLED TO EXERCISE SUCH LEGAL RIGHTS AS IT MAY HAVE BY
BEING A SHAREHOLDER OF SUCH ENTITY.

        7.     Release. Borrower and Guarantors on their own behalf and on
behalf of their predecessors, successors and assigns (collectively, the
“Releasing Parties”), hereby acknowledge and stipulate that as of the date of
the execution of this Third Amendment, none of the Releasing Parties has any
claims or causes of action of any kind whatsoever against Lender or any of its
officers, directors, employees, agents, attorneys, or representatives, or
against any of their respective predecessors, successors, or assigns. Each of
the Releasing Parties hereby forever releases, remises, discharges and holds
harmless Lender and all of its officers, directors, employees, agents,
attorneys, and representatives, and all of their respective predecessors,
successors, and assigns, from any and all claims, causes of action, demands, and
liabilities of any kind whatsoever, whether direct or indirect, fixed or
contingent, liquidated or non-liquidated, disputed or undisputed, known or
unknown, which any of the Releasing Parties has or may acquire in the future
relating in any way to any event, circumstance, action, or failure to act from
the beginning of time through the date of the execution of this Third Amendment.

        8.     Defined Terms. Words and terms used herein which are defined in
the Loan Agreement are used herein as defined therein, except as specifically
modified by the terms of this Third Amendment. Terms used in this Third
Amendment which are not defined in the Loan Agreement are used therein as herein
defined.

        9.     Miscellaneous.

        9.1.     Preservation of the Loan Agreement. Except as specifically
amended and modified by the terms of this Third Amendment, all of the terms,
provisions, covenants, warranties, and agreements contained in the Loan
Agreement, the Guaranty, and in the other Related Documents shall remain in full
force and effect (any irreconcilable conflicts or inconsistencies between the
terms of this Third Amendment and the Loan Agreement, the Guaranty, or any other
Related Document, shall be governed and controlled by this Third Amendment).

        9.2.     Counterparts. This Third Amendment may be executed in two or
more counterparts, and it shall not be necessary that any one of the
counterparts be executed by all of the parties hereto. Each fully or partially
executed counterpart shall be deemed an original, but all such counterparts
taken together shall constitute but one and the same instrument.

        9.3.     Joinder. Each of the Guarantors join in the execution of this
Third Amendment to join in the release set forth in numerical section 6 above
and to evidence that their Guaranty remains in full force and effect and is not
limited or impaired as a result of the execution and delivery of this Third
Amendment by Borrower.

        9.4.     NO ORAL AGREEMENTS. THIS WRITTEN AGREEMENT AND THE OTHER
WRITTEN LOAN DOCUMENTS REPRESENT THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY
NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES. THERE ARE NOT UNWRITTEN ORAL AGREEMENTS BETWEEN THE
PARTIES.

        9.5.     ACKNOWLEDGMENT. BORROWER HAS BEEN ADVISED BY LENDER TO SEEK THE
ADVICE OF AN ATTORNEY AND AN ACCOUNTANT IN CONNECTION WITH THE COMMERCIAL LOANS
EVIDENCED BY THE LETTER OF CREDIT; AND BORROWER HAS HAD THE OPPORTUNITY TO SEEK
THE ADVICE OF AN ATTORNEY AND ACCOUNTANT OF BORROWER’S CHOICE IN CONNECTION WITH
THE COMMERCIAL LOANS EVIDENCED BY THE LETTER OF CREDIT.

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        IN WITNESS WHEREOF, the parties have executed this Third Amendment as of
the date first above written.

POWELL ELECTRICAL SYSTEMS, INC.

By:____________________________________
Name:___________________________
Title:____________________________

                                        BORROWER

BANK OF AMERICA, N.A.

By:______________________________
Name:___________________________
Title:____________________________

                                        LENDER

JOINED IN FOR THE PURPOSES
SET FORTH ABOVE:

POWELL-ESCO COMPANY

By:                                                     
           Don R. Madison,
           Secretary

TRANSDYN CONTROLS, INC.

By:                                                     
           Don R. Madison,
           Secretary

TRACTION POWER SYSTEMS, INC.

By:                                                     
           Don R. Madison,
           Secretary

POWELL INDUSTRIES, INC.

By:                                                     
Name:                                                     
Title:                                                     

GUARANTORS