**Exhibit 10.1****FIFTH AMENDMENT TO CREDIT AGREEMENT**     THIS FIFTH AMENDMENT TO CREDIT AGREEMENT (this “***Amendment***”) is entered into as of December 4,2007, but shall be effective for all purposes as of the Effective Date (defined below) among PowellIndustries, Inc., a Delaware corporation (“***Parent***”), Switchgear & Instrumentation Ltd., an entityorganized under the laws of England and Wales (formerly known as Inhoco 3210 Limited, “***Inhoco***”),Switchgear & Instrumentation Properties Limited, an entity organized under the laws of England andWales (“***SI Properties***” and together with Inhoco, “***UK Borrower***”), Bank of America, N.A., a nationalbanking association, as Agent, Swing Line Lender and L/C Issuer under the Credit Agreement (in suchcapacity as administrative agent, together with its successors in such capacity, “***Agent***”), and eachlender from time to time party to the Credit Agreement (collectively, “***Lenders***” and individually, a“***Lender***”). Capitalized terms used but not defined in this Amendment have the meaning given them inthe Credit Agreement (defined below).**RECITALS**     A. Parent, Inhoco, and SI Properties, as borrowers (each a “***Borrower***” and collectively“***Borrowers***”), Agent and Lenders entered into that certain Credit Agreement dated as of June 29,2005 (as amended by the First Amendment to Credit Agreement dated November 7, 2005, as amended bythe Second Amendment to Credit Agreement dated January 11, 2006, as amended by the Third Amendmentto Credit Agreement dated August 4, 2006, as amended by the Fourth Amendment to Credit Agreementdated December 7, 2006, and as amended, restated or supplemented, the “***Credit Agreement***”).     B. Borrowers, Agent and Lenders have agreed to amend the Credit Agreement, subject to theterms and conditions of this Amendment.     NOW THEREFORE, for good and valuable consideration, the receipt and sufficiency of which areacknowledged, the undersigned hereby agree as follows:     1. Amendment to Credit Agreement. The Credit Agreement is amended as set forth belowas of the Effective Date:     (a) The definition of “Approved Period” in ***Section 1.01***of the Credit Agreement isdeleted in its entirety and replaced with the following:“***Approved Period***means the period commencing on the Closing Date and endingon December 31, 2008 (such period may be extended if requested by UKBorrower and if the Required Lenders agree, in their sole discretion, to anextension in writing).”     (b) ***Section 7.******11(f)*** of the Credit Agreement is deleted in its entirety and replacedwith the following:     “**(f) Capital Expenditures**. Make or become legally obligated to makeany expenditure in respect of the purchase or other acquisition of
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any fixed or capital asset (excluding normal replacements andmaintenance which are properly charged to current operations), except forcapital expenditures in the ordinary course of business not exceeding, inthe aggregate for Parent and its Subsidiaries, for the fiscal years endedSeptember 30, 2006 and September 30, 2007, the amount set forth oppositesuch fiscal year:     Period Ending Maximum Capital ExpendituresSeptember 30, 2006 $8,750,000 September 30, 2007 $15,000,000”     2. Conditions. This Amendment shall be effective as of September 30, 2007 (the“***Effective Date***”) once each of the following have been delivered to Agent: (a) this Amendment executed by Borrowers, Agent and Lenders;  (b) Guarantors’ Consent and Agreement executed by the Guarantors; and  (c) such other documents as Agent or Lenders may reasonably request.     3. Representations and Warranties. Each Borrower represents and warrants to Agent andLenders that (a) it possesses all requisite power and authority to execute, deliver and comply withthe terms of this Amendment, (b) this Amendment has been duly authorized and approved by allrequisite corporate action on the part of Borrower, (c) no other consent of any Person (other thanLenders) is required for this Amendment to be effective, (d) the execution and delivery of thisAmendment does not violate its organizational documents, (e) the representations and warranties ineach Loan Document to which it is a party are true and correct in all material respects on and asof the date of this Amendment as though made on the date of this Amendment (*except*to the extentthat such representations and warranties speak to a specific date), (f) it is in full compliancewith all covenants and agreements contained in each Loan Document (as amended by this Amendment) towhich it is a party, and (g) no Default or Event of Default has occurred and is continuing (otherthan any Default or Event of Default cured by the amendments in Section 1 of this Amendment). Therepresentations and warranties made in this Amendment shall survive the execution and delivery ofthis Amendment. No investigation by Agent or Lenders is required for Agent or Lenders to rely onthe representations and warranties in this Amendment.     4. Scope of Amendment; Reaffirmation; Release. All references to the Credit Agreementshall refer to the Credit Agreement as amended by this Amendment. Except as affected by thisAmendment, the Loan Documents are unchanged and continue in full force and effect. However, in theevent of any inconsistency between the terms of the Credit Agreement (as amended by this Amendment)and any other Loan Document, the terms of the Credit Agreement shall control and such otherdocument shall be deemed to be amended to conform to the terms of the Credit Agreement. Borrowershereby reaffirm their obligations under the Loan Documents to which each is a party and agree thatall Loan Documents to which they are a party remain in full force and effect and continue to belegal, valid, and binding obligations enforceable in accordance with their terms (as the same areaffected by this Amendment).
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Borrowers hereby release Agent and Lenders from any liability for actions or omissions inconnection with the Credit Agreement and the other Loan Documents prior to the date of thisAmendment.     5. Miscellaneous.     (a) Waiver. Lender (i) waives any violation of, or noncompliance with ***Section7.******11(f)*** of the Credit Agreement arising prior to the date hereof, and (ii) agrees not toexercise any of the rights or remedies available to it under the Loan Documents solely as aresult of the violation or noncompliance described in the preceding *clause (i)*. Except asexpressly set forth in the preceding sentence, this Amendment does not constitute (i) awaiver of, or a consent to, (A) any provision of the Credit Agreement or any other LoanDocument not expressly referred to in this Amendment, or (B) any present or future violationof, or default under, any provision of the Loan Documents, or (ii) a waiver of Agent’s orLenders’ right to insist upon future compliance with each term, covenant, condition andprovision of the Loan Documents.     (b) Form. Each agreement, document, instrument or other writing to befurnished to Lenders under any provision of this Amendment must be in form and substancesatisfactory to Agent and its counsel.     (c) Headings. The headings and captions used in this Amendment are forconvenience only and will not be deemed to limit, amplify or modify the terms of thisAmendment, the Credit Agreement, or the other Loan Documents.     (d) Costs, Expenses and Attorneys’ Fees. Borrowers agree to pay or reimburseAgent on demand for all of their reasonable out-of-pocket costs and expenses incurred inconnection with the preparation, negotiation, and execution of this Amendment, including,without limitation, the reasonable fees and disbursements of Agent’s counsel.     (e) Successors and Assigns. This Amendment shall be binding upon and inure tothe benefit of each of the undersigned and their respective successors and permittedassigns.     (f) Multiple Counterparts. This Amendment may be executed in any number ofcounterparts with the same effect as if all signatories had signed the same document. Allcounterparts must be construed together to constitute one and the same instrument. ThisAmendment may be transmitted and signed by facsimile. The effectiveness of any suchdocuments and signatures shall, subject to applicable law, have the same force and effect asmanually-signed originals and shall be binding on Borrowers, Agent and Lenders. Agent mayalso require that any such documents and signatures be confirmed by a manually-signedoriginal; *provided that*the failure to request or deliver the same shall not limit theeffectiveness of any facsimile document or signature.     (g) Governing Law. This Amendment and the other Loan Documents must beconstrued, and their performance enforced, under Texas law.
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     (h) Entirety. **The Loan Documents (as amended hereby) Represent the FinalAgreement Among Borrowers, Agent and Lenders and May Not Be Contradicted by Evidence ofPrior, Contemporaneous, or Subsequent Oral Agreements by the Parties. There Are NoUnwritten Oral Agreements among the Parties.****[Signatures appear on the following pages.]**
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     The Amendment is executed as of the date set out in the preamble to this Amendment.         **BORROWERS:**           **POWELL INDUSTRIES, INC.**           By: /s/ Don R. Madison             Don R. Madison      Executive Vice President, Secretary and      Treasurer           **SWITCHGEAR & INSTRUMENTATION**    **LTD.**, formerly known as Inhoco 3210 Limited           By: /s/ Don R. Madison             Don R. Madison      Director           **SWITCHGEAR & INSTRUMENTATION**    **PROPERTIES LIMITED**           By: /s/ Don R. Madison             Don R. Madison      Director  Signature Page to Fifth Amendment to Credit Agreement
 

 
         **BANK OF AMERICA, N.A.**, as Agent           By: /s/ Daniel J. Lintner             Daniel J. Lintner      Senior Vice President           **BANK OF AMERICA, N.A.**, as a Lender, L/C    Issuer and Swing Line Lender           By: /s/ Daniel J. Lintner             Daniel J. Lintner      Senior Vice President  Signature Page to Fifth Amendment to Credit Agreement
 

 
**GUARANTORS’ CONSENT AND AGREEMENT TO FIFTH AMENDMENT**     As an inducement to Agent and Lenders to execute, and in consideration of Agent’s and Lenders’execution of, this Amendment, the undersigned hereby consents to this Amendment and agrees thatthis Amendment shall in no way release, diminish, impair, reduce or otherwise adversely affect theobligations and liabilities of the undersigned under the Guaranty executed by each of theundersigned in connection with the Credit Agreement, or under any Loan Documents, agreements,documents or instruments executed by the undersigned to create liens, security interests or chargesto secure any of the Obligations (as defined in the Credit Agreement), all of which are in fullforce and effect. The undersigned further represents and warrants to Agent and Lenders that (a)the representations and warranties in each Loan Document to which it is a party are true andcorrect in all material respects on and as of the date of this Amendment as though made on the dateof this Amendment (except to the extent that such representations and warranties speak to aspecific date), (b) it is in full compliance with all covenants and agreements contained in eachLoan Document to which it is a party, and (c) no Default or Event of Default has occurred and iscontinuing. Guarantors hereby release Agent and Lenders from any liability for actions oromissions in connection with the Loan Documents prior to the date of this Amendment. ThisGuarantors’ Consent and Agreement shall be binding upon each of the undersigned, and its permittedassigns, and shall inure to the benefit of Agent, Lenders, and its successors and assigns.**GUARANTORS:**           TRANSDYN, INC.,a Delaware corporation   POWELL INDUSTRIES ASIA, INC.,a Delaware corporation             By: /s/ Don R. Madison Don R. Madison   By: /s/ Don R. Madison Don R. Madison    Vice President, Secretary andTreasurer     Vice President, Secretary andTreasurer             POWELL INDUSTRIES INTERNATIONAL,INC., a Delaware corporation   POWELL ELECTRICAL SYSTEMS, INC.,a Delaware corporation             By: /s/ Don R. Madison Don R. Madison   By: /s/ Don R. Madison Don R. Madison    Vice President, Secretary andTreasurer     Vice President, Secretary andTreasurer  Guarantors’ Consent and Agreement to Fifth Amendment