Document:

EXHIBIT 10.12

                            DEMAND PROMISSORY NOTE

   FOR VALUE RECEIVED, CompuTrac, Inc., a Texas Corporation, hereby  promises
 and agrees to pay to the order of  Harry W. Margolis, his heirs or  assigns,
 the sum of Eight Hundred Seventeen  Thousand Six Hundred and Fifty Nine  and
 no/100 Dollars ($817,659.00), together with interest thereon at the rate  of
 six percent (6%)   per  annum on the  unpaid balance  beginning February  1,
 2001.  Said sum shall be paid in the manner following:

   1) all accrued interest shall be paid monthly commencing March 1, 2001,
      and continuing on the first day of each calendar month thereafter;

   2) the principal shall be payable on demand, which may be made in whole
      or in part, or if no demand is made, then on January 1, 2003.

   All  payments shall  be  first applied  to  interest and  the  balance  to
 principal.  This  Note may  be prepaid at  any time,  in whole  or in  part,
 without penalty.

   Further, this Note shall, at the option of the holder, be immediately  due
 and payable upon  failure to  make any payment  due hereunder,  or upon  the
 occurrence of any one or more of the following events:

 1.) breach of any condition in any security interest, mortgage, pledge
     agreement or guaranty granted now or in the future as collateral
     security for this Note; or,

 2.) breach of any existing or future condition in any security agreement or
     mortgage, if any, having a priority over any security agreement or
     mortgage on collateral granted, in whole or in part, as collateral
     security for this Note; or,

 3.) upon the filing by the undersigned, or any future obligor hereof,  an
     assignment for the benefit of creditors, bankruptcy or for relief under
     any provisions of the Bankruptcy Code; or by suffering an involuntary
     petition in bankruptcy or receivership not vacated within thirty (30)
     days.

   The  failure of the holder to accelerate or  demand payment shall not  act
 as  a waiver as to  any subsequent or other  event which would authorize the
 acceleration or demand  for payment,  nor shall any  such failure  act as  a
 waiver to  accelerate  or demand  payment  due  to the  continuance  of  the
 condition or ongoing status initially brought about by the occurrence of any
 such event.

   In the  event this Note shall  be in default and  placed with an  attorney
 for collection, then  the undersigned agrees  to pay all  attorney fees  and
 costs of collection incurred by the holder.  All payments hereunder shall be
 made in Dallas County, Texas or to such address as may from time-to-time  be
 designated in writing by any holder hereof.

   The undersigned and all other parties to this Note, whether as  endorsers,
 guarantors or sureties, waive demand, presentment and protest of all notices
 thereto and further  agree to remain  bound, notwithstanding any  extension,
 modification, waiver,  or  other  indulgence  by  any  holder  or  upon  the
 discharge or release of any obligor hereunder  or to this Note, or upon  the
 exchange, substitution or release of any collateral granted as security  for
 this Note.

   Signed and dated this 31st day of January, 2001.

                               CompuTrac, Inc.

                               By:_______________________________
                                    George P. Pardue
                               Its: Chief Financial Officer<PAGE>

                                                                  EXHIBIT 10.20
                                                                  -------------

                            THIRD AMENDMENT TO THE
                     BENTHOS, INC. 401(K) RETIREMENT PLAN

Benthos, Inc. (the "Employer") having heretofore adopted the Benthos, Inc.
401(k) Retirement Plan, a prototype plan document consisting of the Plan
Agreement #001 and the Putnam Basic Plan Document #07 (the "Plan") effective as
of July 1, 1999, pursuant to the power reserved to the Employer in Section 17.1
of the Plan, hereby amends the Plan Agreement as set forth below.

1.   Subsection E. of Section 1., of the Plan Agreement is hereby amended
     effective October 1, 2000, by striking said subsection in its entirety and
     by substituting the following new paragraph in lieu thereof:

     "E.  Employer Contract:        Name:    Francis E. Dunne, Jr.
          -----------------                  ---------------------
                                    Title:   Vice President, CFO, Treasurer
                                             ------------------------------
                                    Phone #: 508-563-1000
                                             ------------

                                    Name:    Robert J. Mulvaney
                                             ------------------
                                    Title:   Controller
                                             ----------
                                    Phone #: 508-563-1000"
                                             ------------

2.  In all other respects, the Plan provisions remain in full force and effect.

IN WITNESS WHEREOF, the Employer has caused the Third Amendment to the Plan to
be duly executed in its name and behalf and its corporate seal to be affixed as
of the date signed below.

<TABLE>
<CAPTION>
ATTEST:
<S>              <C>                             <C>
BENTHOS, INC.                                    PUTNAM FIDUCIARY TRUST COMPANY
By:   /s/ Francis E. Dunne, Jr.                  By:  /s/ Tina A. Campbell
     ------------------------------                  -------------------------------
Print Name:  Francis E. Dunne, Jr.               Print Name:  Tina A. Campbell
             ------------------------------                   -----------------------------
Title:       Vice President, CFO, Treasurer      Title:       SVP Compliance and Consulting
             ------------------------------                   -----------------------------
Date:        2/8/01                              Date:        2/27/01
             ------------------------------                   -----------------------------
</TABLE><PAGE>

                                                                  EXHIBIT 10.33
                                                                  -------------

                      FIRST AMENDMENT TO CREDIT AGREEMENT
                 AND AMENDMENT TO REVOLVING NOTE AND TERM NOTE
                 ---------------------------------------------

     This First Amendment to Credit Agreement and Amendment to Revolving Note
and Term Note is made as of this 23rd day of March, 2001, by and between Cape
Cod Bank and Trust Company ("Lender"), a Massachusetts banking corporation, with
a principal place of business at 2 Barlows Landing Road, Pocasset, Massachusetts
02559 and Benthos, Inc. ("Borrower"), a Massachusetts corporation with its
principal place of business at 49 Edgerton Drive, North Falmouth, Massachusetts
02556.

                                R E C I T A L S:
                                - - - - - - - -

     A.  Borrower and Lender entered into a certain Credit Agreement dated
August 18, 1999 regarding certain Revolving Loans and a Term Loan as defined
therein, pursuant to which Borrower executed and delivered to Lender a Revolving
Note and a Term Note;

     B.  Borrower and Lender have previously amended the Revolving Note pursuant
to an Amendment of Promissory Note dated December 8, 2000, and amended the Term
Note pursuant to an Amendment of Commercial Variable Rate Promissory Note dated
October 17, 2000.

     C.  Borrower and Lender now desire to amend the Credit Agreement and to
further amend each of the Revolving Note and the Term Note as set forth herein
and simultaneously herewith Borrower and Lender shall execute and deliver a
Second Amendment To Commercial Variable Rate Revolving or Draw Note in the form
of Exhibit A attached hereto and a Second Amendment to Commercial Variable Rate
Promissory Note in the form of Exhibit B attached hereto.

                              A G R E E M E N T S:
                              - - - - - - - - - -

     Now, therefore, in consideration of the foregoing and for other good and
valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the Lender and the Borrower hereby agree as follows:

     1.  Capitalized terms used herein shall have the meaning given to them in
the Credit Agreement unless separately defined herein.

     2.  As of March 22, 2001, the outstanding principal balance of this
Revolving Loan under the Revolving Note is Three Hundred Thousand Dollars
($300,000.00) and the outstanding principal balance of the Term Loan under the
Term Note is Four Million Two Hundred Fifty-Five Thousand Nine Hundred Fifty-Two
and 39/100 Dollars ($4,255,952.39).

     3.  The Expiration Date of the Revolving Loan (and the maturity date of the
Revolving Note) is hereby extended to January 31, 2002.
<PAGE>

     4.  The Revolving Commitment Amount is hereby reduced from Two Million
Dollars ($2,000,000.00) to Seven Hundred Thousand Dollars ($700,000.00).

     5.  The rate of interest payable on the Revolving Loans is hereby changed
to a variable rate per annum equal to the Prime Rate plus one and one-half
percent (1  1/2%).  Accordingly, the second sentence of Section 2.04(a) of the
Credit Agreement is hereby deleted and replaced with the following:  "The rate
of interest so payable shall be a fluctuating rate per annum which at all times
shall be equal to the sum of the Prime Rate plus one and one-half percent (1
1/2%), but, in no event, in excess of the maximum rate then permitted by
applicable law, with a change in such rate to become effective on the same day
on which any change in the Prime Rate is effective."

     6.  The rate of interest payable on the Term Loan is hereby changed to a
variable rate per annum equal to the Prime Rate plus one-half percent ( 1/2%).

     7.  Section 8.02 of the Credit Agreement is hereby deleted in its entirety
and replaced with the following:

     "Section 8.02.  Financial Covenants.
                     -------------------

               The Borrower covenants and agrees that, so long as any loan is
          outstanding or any obligation of the Borrower to the Lender, in any
          capacity, remains unpaid, or any commitment by the Lender to the
          Borrower is in effect:

          a.   The Borrower will maintain a ratio of Current Assets to Current
               Liabilities of greater than or equal to 1.50 to 1.00;

          b.   The Borrower shall maintain a ratio of Total Debt to Tangible Net
               Worth less than or equal to 2.00 to 1.00; and

          c.   The Borrower shall maintain a ratio of Cash Flow to Debt Service
               Payments, which on a cumulative basis for the applicable calendar
               year, shall be greater than or equal to the following:

                    (i)    -.50 to 1.00 as of  March 31, 2001;

                    (ii)   .34  to 1.00 as of  June 30, 2001; and

                    (iii)  .74 to 1.00 as of September 30, 2001 and thereafter.

          d.   Borrower shall monthly, on or before the fifteenth (15th) of each
               month for the immediately prior month, provide to Lender an
               accounts receivable aging report, an inventory report and a
               backlog backlog report.

                                       2
<PAGE>

     8.  Except as provided herein, the Credit Agreement shall remain unchanged
and as amended hereby, the Credit Agreement is hereby ratified and confirmed.

Witness:            BENTHOS, INC.

/s/ Francis E. Dunne, Jr.        By: /s/ Stephen D. Fantone
                                     -------------------------
                                     Name:  Stephen D. Fantone
                                     Title: President & CEO

Witness:  CAPE COD BANK AND TRUST  COMPANY

/s/ Stephen Sooy                 By: /s/ Timothy F. Kelleher
-----------------                    ----------------------------
                                     Name:  Timothy F. Kelleher
                                     Title: Senior Vice President

                                       3

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