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FOURTH AMENDMENT TO CREDIT AGREEMENTGUARANTORS’ CONSENT AND AGREEMENT TO FOURTH AMENDMENT

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**FOURTH AMENDMENT TO CREDIT AGREEMENT**     THIS FOURTH AMENDMENT TO CREDIT AGREEMENT (this “***Amendment***”) is entered into as ofDecember 7, 2006, but shall be effective for all purposes as of the Effective Date (definedbelow) among Powell Industries, Inc., a Delaware corporation (“***Parent***”), Switchgear &Instrumentation Ltd., an entity organized under the laws of England and Wales (formerly known asInhoco 3210 Limited, “***Inhoco***”), Switchgear & Instrumentation Properties Limited, an entityorganized under the laws of England and Wales (“SI Properties” and together with Inhoco, “***UKBorrower***”), Bank of America, N.A., a national banking association, as Agent, Swing Line Lender andL/C Issuer under the Credit Agreement (in such capacity as administrative agent, together with itssuccessors in such capacity, “***Agent***”), and each lender from time to time party to the CreditAgreement (collectively, “***Lenders***” and individually, a “***Lender***”). Capitalized terms used but notdefined in this Amendment have the meaning given them in the 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, and as amended, restated or supplemented, the “***CreditAgreement***”).     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:“***ApprovedPeriod*** means the period commencing on the Closing Date and endingon December 31, 2007 (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(c)*** of the Credit Agreement is deleted in its entirety and replacedwith the following:     **“(c)     MinimumTangible Net Worth.** Permit Consolidated Tangible NetWorth as of the end of each fiscal quarter, commencing with the quarterending September 30, 2006, to be less than the *sum* of (i)
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$120,000,000*plus* (ii) an amount equal to 50% of the Consolidated NetIncome for each fiscal quarter, commencing with the fiscal quarter endingSeptember 30, 2006, and for each fiscal quarter thereafter (with nodeduction for a net loss in any fiscal quarter), *plus* (iii) an amount equalto 100% of the aggregate increases in Shareholders’ Equity of Parent and itsSubsidiaries after the date hereof by reason of the issuance and sale of anyEquity Interests of Parent or any Subsidiary (other than issuances to Parentor a wholly-owned Subsidiary), including upon any conversion of debtsecurities of Parent into such capital stock or other equity interests.”(c)     ***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 any fixedor capital asset (excluding normal replacements and maintenance which areproperly charged to current operations), except for capital expenditures inthe ordinary course of business not exceeding, in the aggregate for Parentand it Subsidiaries, for the fiscal years ended September 30, 2006 andSeptember 30, 2007, the amount set forth opposite such fiscal year:          Period Ending  Maximum Capital Expenditures   September 30, 2006   $8,750,000   September 30, 2007   $13,000,000”        2.     Conditions. This Amendment shall be effective as of September 30, 2006 (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 thisAmendment (*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
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in Section 1 of this Amendment). The representations and warranties made in this Amendmentshall survive the execution and delivery of this Amendment. No investigation by Agent or Lendersis required for Agent or Lenders to rely on the 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). Borrowers hereby release Agent and Lenders from any liability foractions or omissions in connection with the Credit Agreement and the other Loan Documents prior tothe date of this Amendment.     5.     Miscellaneous.     (a) Waiver. Lender (i) waives any violation of, or noncompliance with ***Section7.11(c)*** and ***Section 7.11(f)*** of the Credit Agreement arising prior to the date hereof, and(ii) agrees not to exercise any of the rights or remedies available to it under the LoanDocuments solely as a result of the violation or noncompliance described in the preceding*clause (i)*. Except as expressly set forth in the preceding sentence, this Amendment doesnot constitute (i) a waiver of, or a consent to, (A) any provision of the Credit Agreementor any other Loan Document not expressly referred to in this Amendment, or (B) any presentor future violation of, or default under, any provision of the Loan Documents, or (ii) awaiver of Agent’s or Lenders’ right to insist upon future compliance with each term,covenant, condition and provision 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.
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     (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.     (h) Entirety. **The Loan Documents (as amended hereby) Representthe Final Agreement Among Borrowers, Agent and Lenders and May Not Be Contradicted byEvidence of Prior, Contemporaneous, or Subsequent Oral Agreements by the Parties. There AreNo Unwritten 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