MCFSA,
      Ltd.

     

    UNSECURED
      PROMISSORY NOTE

     

    
       

      
        	$250,000.00	
                 January
                  1, 2008

              
	 	 
	 	
                San
                  Antonio,
                  Texas

              


      

    

     

    FOR
      VALUE
      RECEIVED, MCFSA, Ltd., a Texas limited partnership (the “Company”)
      promises to pay to Fire Quest, Inc., a Texas corporation (“Seller”),
      or
      its registered assigns, in lawful money of the United States of America the
      principal sum of TWO HUNDRED FIFTY THOUSAND AND NO/100 ($250,000.00), or such
      lesser amount as shall equal the outstanding principal amount hereof, together
      with interest from the date of this Note on the unpaid principal balance at
      a
      rate equal to 7.25
      % per
      annum, computed on the basis of the actual number of days elapsed and a year
      of
      365 days. All unpaid principal, together with any then unpaid and accrued
      interest and other amounts payable hereunder, shall be due and payable on
      (i) January 1, 2009 (the “Maturity
      Date”),
      or
      (ii) when, upon or after the occurrence of an Event of Default (as defined
      below), such amounts are declared due and payable by Seller or made
      automatically due and payable in accordance with the terms hereof. Until the
      Maturity Date, payments shall be due and payable in accordance with the Payment
      Schedule attached hereto as Schedule
      A.
      This
      Note is issued pursuant to the Asset Purchase Agreement effective January 1,
      2008 (as
      previously or hereafter amended, modified or supplemented, the “Purchase
      Agreement”)
      between the Company and the Seller, and is guarantied by affiliates of the
      Company pursuant to Guaranty Agreements of even date herewith.

     

    The
      following is a statement of the rights of Seller and the conditions to which
      this Note is subject, and to which Seller, by the acceptance of this Note,
      agrees:

     

    1. Definitions.
      As used
      in this Note, the following capitalized terms have the following
      meanings:

     

    (a) “Company”
      includes the corporation initially executing this Note and any Person which
      shall succeed to or assume the obligations of the Company under this
      Note.

     

    (b) “Event
      of Default”
has
      the
      meaning given in Section 5
      hereof.

     

    (c) “Seller”
shall
      mean the Person specified in the introductory paragraph of this Note or any
      Person who shall at the time be the registered holder of this Note.

     

    (d) “Purchase
      Agreement”
has
      the
      meaning given in the introductory paragraph hereof.

     

    (e) “Obligations”
shall
      mean and include all loans, advances, debts, liabilities and obligations,
      howsoever arising, owed by the Company to Seller of every kind and description
      (whether or not evidenced by any note or instrument and whether or not for
      the
      payment of money), now existing or hereafter arising under or pursuant to the
      terms of this Note, including, all interest, fees, charges, expenses, attorneys’
fees and costs and accountants’ fees and costs chargeable to and payable by the
      Company hereunder, in each case, whether direct or indirect, absolute or
      contingent, due or to become due, and whether or not arising after the
      commencement of a proceeding under Title 11 of the United States Code (11
      U.S.C. Section 101 et
      seq.),
      as
      amended from time to time (including post-petition interest) and whether or
      not
      allowed or allowable as a claim in any such proceeding.

     

    
      
         

      

      
         

        
          

        

      

      
         

      

    

     

    (f) “Person”
shall
      mean and include an individual, a partnership, a corporation (including a
      business trust), a joint stock company, a limited liability company, an
      unincorporated association, a joint venture or other entity or a governmental
      authority.

     

    (g) “Securities
      Act”
shall
      mean the Securities Act of 1933, as amended.

     

    (h) “Senior
      Indebtedness”
means,
      unless expressly subordinated to or made on a parity with the amounts due under
      this Note, the principal of (and premium, if any), unpaid interest on, amounts
      reimbursable, fees, expenses, costs of enforcement and any other amounts due
      in
      connection with (i) indebtedness of the Company, or with respect to which the
      Company is a guarantor, to banks or other lending institutions regularly engaged
      in the business of lending money, which is for money borrowed, or purchase
      or
      leasing of equipment in the case of lease or other equipment financing, whether
      or not secured, and (ii) any such indebtedness or any notes or other evidence
      of
      indebtedness issued in exchange for such Senior Indebtedness, or any
      indebtedness arising from the satisfaction of such Senior Indebtedness by a
      guarantor.

     

    (i) “Subsidiary”
shall
      mean (a) any corporation of which more than 50% of the issued and
      outstanding equity securities having ordinary voting power to elect a majority
      of the Board of Directors of such corporation is at the time directly or
      indirectly owned or controlled by the Company, (b) any partnership, joint
      venture, or other association of which more than 50% of the equity interest
      having the power to vote, direct or control the management of such partnership,
      joint venture or other association is at the time directly or indirectly owned
      and controlled by the Company, (c) any other entity included in the
      financial statements of the Company on a consolidated basis.

     

    2. Interest.
      Accrued
      and unpaid interest on this Note shall be paid as set forth in Part 1 of
      Schedule A attached hereto, and in addition, at maturity until the outstanding
      principal amount hereof shall be paid in full at maturity.

     

    3. Prepayment.
      This
      Note may be prepaid at any time after February 28, 2008 without consent of
      the
      Seller.

     

    4. Subordination.
      

     

    (a) General
      Subordination.
      The
      indebtedness evidenced by this Note is hereby expressly subordinated in right
      of
      payment to the prior payment in full of all of the Company’s Senior
      Indebtedness, whether now or hereafter existing, as such agreement may be
      supplemented, modified, restated or amended from time to time. Seller hereby
      agrees to execute and deliver such documents as may be reasonably requested
      from
      time to time by the Company or a holder of any Senior Indebtedness, including
      customary forms of subordination agreement requested from time to time by a
      holder of Senior Indebtedness, in order to implement Section 4 hereof. The
      Company may require that the Seller execute such documents as a condition to
      the
      Seller’s rights hereunder.

     

    
      
         

      

      
        -2-

        
          

        

      

      
         

      

    

     

    (b) Specific
      Subordination. The
      obligations evidenced hereby are subordinate in the manner and to the extent
      set
      forth in that certain Subordination Agreement (the “Subordination Agreement”)
      created as of January 1, 2008, among, without limitation, Fire Quest, Inc.,
      a
      Texas corporation (“Subordinated Lender”), MCFSA, LTD., a Texas limited
      partnership and LaSalle Bank National Association, a national banking
      association (“Senior Lender”) to the obligations (including interest) owed by
      ISI Security Group, Inc., formerly known as ISI Detention Contracting Group,
      Inc, a Delaware corporation (“ISI”) to the holders of all of the notes issued
      pursuant to that certain Loan and Security Agreement dated as of October 21,
      2004, between ISI and Senior Lender, as such Agreement may be supplemented,
      modified, restated or amended from time to time; and each holder hereof, by
      its
      acceptance hereof, shall be bound by the provisions of the Subordination
      Agreement.

     

    5. Events
      of Default.
      The
      occurrence of any of the following shall constitute an “Event
      of Default”
under
      this Note:

     

    (a) Failure
      to Pay.
      The
      Company shall fail to pay (i) when due any principal or interest payment on
      the due date hereunder or (ii) any other payment required under the terms
      of this Note on the date due and such payment shall not have been made within
      five days of the Company’s receipt of Seller’s written notice to the
      Company of such failure to pay; or

     

    (b) Voluntary
      Bankruptcy or Insolvency Proceedings. The
      Company shall (i) apply for or consent to the appointment of a receiver,
      trustee, liquidator or custodian of itself or of all or a substantial part
      of
      its property, (ii) be unable, or admit in writing its inability, to pay its
      debts generally as they mature, (iii) make a general assignment for the
      benefit of its or any of its creditors, (iv) be dissolved or liquidated,
      (v) become insolvent (as such term may be defined or interpreted under any
      applicable statute), (vi) commence a voluntary case or other proceeding
      seeking liquidation, reorganization or other relief with respect to itself
      or
      its debts under any bankruptcy, insolvency or other similar law now or hereafter
      in effect or consent to any such relief or to the appointment of or taking
      possession of its property by any official in an involuntary case or other
      proceeding commenced against it, or (vii) take any action for the purpose
      of effecting any of the foregoing; or

     

    (c) Involuntary
      Bankruptcy or Insolvency Proceedings. Proceedings
      for the appointment of a receiver, trustee, liquidator or custodian of the
      Company or of all or a substantial part of the property thereof, or an
      involuntary case or other proceedings seeking liquidation, reorganization or
      other relief with respect to the Company or the debts thereof under any
      bankruptcy, insolvency or other similar law now or hereafter in effect shall
      be
      commenced and an order for relief entered or such proceeding shall not be
      dismissed or discharged within 30 days of commencement.

     

    6. Rights
      of Seller upon Default.
      Upon
      the occurrence or existence of any Event of Default (other than an Event of
      Default described in Sections 5(b)
      or
5(c))
      and at
      any time thereafter during the continuance of such Event of Default, Seller
      may,
      by written notice to the Company, declare all outstanding Obligations payable
      by
      the Company hereunder to be immediately due and payable without presentment,
      demand, protest or any other notice of any kind, all of which are hereby
      expressly waived. Upon the occurrence or existence of any Event of Default
      described in Sections 5(b)
      and
5(c), immediately
      and without notice, all outstanding Obligations payable by the Company hereunder
      shall automatically become immediately due and payable, without presentment,
      demand, protest or any other notice of any kind, all of which are hereby
      expressly waived. In addition to the foregoing remedies, upon the occurrence
      or
      existence of any Event of Default, Seller may exercise any other right power
      or
      remedy permitted to it by law, either by suit in equity or by action at law,
      or
      both. 

     

    
      
         

      

      
        -3-

        
          

        

      

      
         

      

    

     

    7. Successors
      and Assigns.
      Subject
      to the restrictions on transfer described in Sections 10
      and
11
      below,
      the rights and obligations of the Company and Seller shall be binding upon
      and
      benefit the successors, assigns, heirs, administrators and transferees of the
      parties.

     

    8. Waiver
      and Amendment.
      Any
      provision of this Note may be amended, waived or modified upon the written
      consent of the Company and Seller.

     

    9. Assignment
      by the Seller.
      Neither
      this Note nor any of the rights, interests or obligations hereunder may be
      assigned, in whole or in part, by the Company without the prior written consent
      of the Seller, which shall not be unreasonably withheld.

     

    10. Assignment
      by the Company.
      Neither
      this Note nor any of the rights, interests or obligations hereunder may be
      assigned, in whole or in part, by the Company without the prior written consent
      of the Seller, which shall not be unreasonably withheld.

     

    11. Notices.
      All
      notices, requests, demands, consents, instructions or other communications
      required or permitted hereunder shall in writing and faxed, mailed or delivered
      to each party at the respective addresses of the parties as set forth below,
      or
      at such other address or facsimile number as shall have been furnished to the
      receiving party in writing. All such notices and communications will be deemed
      effectively given the earlier of (i) when received, (ii) when
      delivered personally, (iii) one business day after being delivered by
      facsimile or by email (with evidence of delivery or confirmation), (iv) one
      business day after being deposited with a reliable overnight courier service,
      or
      (v) four days after being deposited in the U.S. mail, first class with
      postage prepaid.


    

      
        	
                If
                  to the Company:

              	 	
                MCFSA,
                  Ltd.

              
	 	 	
                12903
                  Delivery Drive

              
	 	 	
                San
                  Antonio, TX 78247

              
	 	 	
                Attention:
                  Sam Youngblood

              
	 	 	
                Facsimile:
                  (210) 495-5613

              
	 	 	
                email:
                  syoungblood@isidet.com

              


      

    

    
      
         

      

      
        -4-

        
          

        

      

      
         

      

    

    

      
        	
                with
                  a copy to:

              	 	
                K&L
                  Gates

              
	 	 	
                111
                  Congress Avenue, Suite 900

              
	 	 	
                Austin,
                  Texas 78701

              
	 	 	
                Attention:
                  D. Hull Youngblood, Jr.

              
	 	 	
                Facsimile:
                  (512) 482-6859

              
	 	 	
                email:
                  hull.youngblood@klgates.com

              
	 	 	 
	 	 	 
	
                If
                  to Seller:

              	 	
                Fire
                  Quest, Inc.

              
	 	 	
                7823
                  Fortune Drive

              
	 	 	
                San
                  Antonio, TX 78520

              
	 	 	
                Attn:
                  William L. Cavin

              
	 	 	 
	 	 	 
	 	 	 
	 	 	 
	
                with
                  a copy to:

              	 	
                James
                  M. Hughes

              
	 	 	
                1100
                  N.E. Loop 410, Suite 900

              
	 	 	
                San
                  Antonio, TX 78209

              
	 	 	
                email:
                  j_hughes@tetco.com

              
	 	 	
                Facsimile:
                  210-930-3073

              


      

    

     

    12. Usury.
      In the
      event any interest is paid on this Note which is deemed to be in excess of
      the
      then legal maximum rate, then that portion of the interest payment representing
      an amount in excess of the then legal maximum rate shall be deemed a payment
      of
      principal and applied against the principal of this Note.

     

    13. Waivers.
      The
      Company hereby waives notice of default, presentment or demand for payment,
      protest or notice of nonpayment or dishonor and all other notices or demands
      relative to this instrument.

     

    14. Governing
      Law.
      This
      Note and all actions arising out of or in connection with this Note shall be
      governed by and construed in accordance with the laws of the State of Texas,
      without regard to the conflicts of law provisions of the State of Texas, or
      of
      any other state.

     

    [Signature
      Page Follows]

     

    
      
         

      

      
        -5-

        
          

        

      

      
         

      

    

     

    The
      Company has caused this Note to be issued as of the date first written
      above.

     

    
      	 	 	 
	 	MCFSA, Ltd., a Texas limited
              partnership
	 	 
	 	
              By: Metroplex Commercial Fire and Security Alarms,
                Inc.

              Its: Sole General Partner

            
	 
 	 
 	 
 
	
            	By:  	/s/
              Sam
              Youngblood 
	 	
              
Sam
              Youngblood, Chief Executive
              Officer


    

    
 

    
      
         

      

      
         

        
          

        

      

      
         

      

    

     

    Schedule
      A

     

    Payment
      Schedule 

     

    Part
      1.
      Quarterly payments of accrued and unpaid interest, to be paid as
      follows:

       

    
      	
              Due
                Date

            	 	
              Amount 

            	 	
               Prin
                Bal

            	 
	
              April
                1, 2008

            	 	
              $

            	
              4,531.25

            	 	
              $

            	
              250,000.00

            	 
	
              July
                1, 2008

            	 	
              $

            	
              4,531.25

            	 	
              $

            	
              250,000.00

            	 
	
              October
                1, 2008

            	 	
              $

            	
              4,531.25

            	 	
              $

            	
              250,000.00

            	 


    

     

    Part
      2.
      One final payment on the Maturity Date equal to the unpaid principal, together
      with any then unpaid and accrued interest and other amounts payable
      hereunder.

     

    
      
         

      

      
        -2-