FIRST AMENDMENT TO CREDIT AGREEMENT, MASTER REAFFIRMATION AND JOINDER TO LOAN DOCUMENTS

Exhibit 10.1

FIRST AMENDMENT TO CREDIT AGREEMENT,

MASTER REAFFIRMATION AND JOINDER TO LOAN DOCUMENTS

This FIRST AMENDMENT TO CREDIT AGREEMENT, MASTER REAFFIRMATION AND JOINDER TO LOAN DOCUMENTS (this “Agreement”) is made as of this 6th day of March, 2006, among DEVCON SECURITY HOLDINGS, INC., a Florida corporation (“Holdings”), DEVCON SECURITY SERVICES CORP., a Delaware Corporation (“Services”), COASTAL SECURITY COMPANY, a Delaware corporation (“Coastal”), COASTAL SECURITY SYSTEMS, INC., a Delaware corporation (“Systems”), CENTRAL ONE, INC., a Florida corporation (“Central One”), GUARDIAN INTERNATIONAL INC., a Florida corporation (“Guardian”), MUTUAL CENTRAL ALARM SERVICES INC., a New York corporation (“Mutual”), STAT-LAND BURGLAR ALARM SYSTEMS & DEVICES INC., a New York corporation (“Stat-Land”), PRECISION SECURITY SYSTEMS, INC., a Florida corporation (“Precision”, and together with Holdings, Services, Coastal, Systems, Central One, Guardian, Mutual and Stat-Land, the “Borrowers”) are sometimes hereinafter referred to individually as a “Borrower” and collectively as “Borrowers”), and CAPITALSOURCE FINANCE LLC, as Agent (in such capacity, the “Agent”), for the Lenders parties thereto and as a Lender. All capitalized terms used but not defined herein shall have the respective meanings ascribed to such terms in the Credit Agreement described below.

W I T N E S S E T H:

A. Holdings, Services, Coastal, Systems and Central One (collectively, the “Existing Borrowers”), Agent and Lenders have entered into that certain Credit Agreement dated as of November 10, 2005 (such Credit Agreement, as the same as amended hereby and as may from time to time be further amended, restated, supplemented or otherwise modified, the “Credit Agreement”), pursuant to which Agent and Lenders made loans and other financial accommodations (collectively, the “Loans”) to Existing Borrowers, subject to the terms and conditions set forth in the Credit Agreement.

B. The Existing Borrowers have entered into various agreements, documents and instruments in connection with the Credit Agreement (collectively, the “Loan Documents”).

C. Devcon International Corp., Devcon Acquisition, Inc. (“Acquisition”) and Guardian have entered into that certain Agreement and Plan of Merger dated November 9, 2005 (“Merger Agreement”),pursuant to which Acquisition will merge with and into Guardian with Guardian as the survivor and concurrently therewith, Guardian will become a Subsidiary of Holdings (the “Merger”).

D. It is a condition to the continuing extension of Loans and other financial accommodations by the Lenders under the Credit Agreement that Guardian, Mutual, Stat-Land and Precision be joined as parties to the Credit Agreement and each other Loan Document and that Existing Borrowers enter into this Agreement to acknowledge and agree that the Loan Documents, and the liens, security interests and guarantees granted and issued thereunder, secure and guaranty the “Obligations” of the Borrowers under the Credit Agreement.

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E. Borrowers have requested that the Credit Agreement be amended as set forth herein to reflect the joinder of Guardian, Mutual, Stat-Land and Precision as parties to the Loan Documents and to increase the Commitment to $100,000,000, and Agent and the Lenders are, subject to the terms hereof, willing to so amend the Credit Agreement.

NOW, THEREFORE, in consideration of the premises set forth herein and for other good and valuable consideration, the receipt and sufficiency of which hereby are acknowledged, each of the undersigned hereby agrees as follows:

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Schedule 1

“Attrition Ratio” shall mean, for any period of determination the ratio of the following (x) and (y), each without duplication, expressed as a percentage: (x) the sum of (i) Attrited RMR (exclusive of Wholesale RMR) for the Measured Time Period and (ii) “Wholesale Attrited RMR” (defined as the net loss, if any, of Wholesale RMR during the Measured Time Period) for the Measured Time Period, divided by (y) the average BOM RMR for the Measured Time Period, with the resulting percentage annualized by multiplying it by the quotient of twelve (12) divided by the number of months in the Measured Time Period.

“First Amendment” means the First Amendment to Credit Agreement, Master Reaffirmation and Joinder to Loan Documents dated as of March 6, 2006, among Borrowers, Agent and Lenders.

“Preferred Stock” means the Series A Convertible Preferred Stock, par value $0.10 per share of Parent.

“The Borrowers shall utilize the proceeds of the Loans as set forth in Recital B. Disclosure Schedule (2.3) contains a description of the Borrowers’ sources and uses of funds as of the Closing Date and the date of First Amendment, including the Advance to be made or incurred on such dates, and a funds flow memorandum detailing how funds from each source are to be transferred and particular uses.”

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“No such Borrower shall make any Restricted Payment, except: (a) intercompany loans and advances among the Borrowers to the extent permitted by Section 7.3; (b) dividends and distributions to another Borrower and dividends to Holdings in an amount required by Holdings to dividend to Parent to permit Parent to pay dividends on the Preferred Stock as set forth in the Certificate of Designations for the Preferred Stock filed by Parent with the Secretary of State of Florida; (c) employee loans permitted under Section 7.4(b); (d) payments of principal and interest of Intercompany Notes issued in accordance with Section 7.3; and (e) any payment of reasonable and customary expenses to the Parent or any Borrower or Affiliate thereof, so long as such expenses are paid in the ordinary course of business, on an arm’s length basis, in an aggregate amount not to exceed $360,000 plus the amount of any reasonable out-of-pocket expenses incurred in connection with the management of Borrowers in any Fiscal Year; and provided that no Event of Default exists or would occur before or after giving effect to any such proposed payment in clauses (a) through (e) of this Section.”

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each Loan Document to which it is a party, and (ii) to the extent such Person granted Liens on or security interests in any of the Collateral pursuant to any Loan Document as security for the Obligations and the obligations, liabilities and indebtedness of such Person under or with respect to the Loan Documents, ratifies and reaffirms such grant of security and confirms and agrees that such Liens and security interests hereafter secure all of the Obligations and the other obligations, indebtedness and liabilities of such Person and the other Borrowers, as applicable, under the Loan Documents.

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[Signature Page Follows]

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IN WITNESS WHEREOF, this Agreement has been duly executed by each of the undersigned as of the day and year first set forth above.

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