**Exhibit
      10.13**





**LOAN
      MODIFICATION AGREEMENT**




March 30,
              2006




THIS
      AGREEMENT is by and among Wainwright Bank & Trust Company, having an office
      at 63 Franklin Street, Boston, Massachusetts 02110 (the “Bank”), and Zoom
      Telephonics, Inc., a Delaware corporation, having a principal place of business
      and chief executive office at 207 South Street, Boston, Massachusetts 02111
      (the
“Borrower”).





Recitals





A.  
      The Bank is the holder of a Commercial Real Estate Promissory Note from the
      Borrower dated January 10, 2001, in the original principal amount of
      $6,500,000.00, as amended by First Amendment to Commercial Real Estate
      Promissory Note dated March 28, 2005 (the “Note”). The Note is secured, in part,
      by that certain Mortgage, Security Agreement and Assignment from the Borrower
      to
      the Bank dated January 10, 2001, and recorded with the Suffolk County Registry
      of Deeds in Book 25763, Page 284, and filed with the Suffolk County Registry
      District of the Land Court (the “Registry District”) as Document No. 609541 (the
“Mortgage”), which Mortgage covers the land and premises known as and located at
      195-201 South Street, 50 Utica Street, 207-209 South Street, and 162-168
      Kneeland Street, Boston, Massachusetts (the “Mortgaged Property”). The Note, the
      Mortgage, and all other instruments, including but not limited to, an Assignment
      of Leases and Rents from the Borrower to the Bank dated January 10, 2001, and
      recorded with the Suffolk County Registry of Deeds in Book 25763, Page 315,
      and
      filed with the Registry District as Document No. 609542, given to the Bank
      heretofore or hereafter as security for the Note or in connection with the
      indebtedness evidenced thereby are herein referred to collectively as the “Loan
      Documents”. All capitalized terms used herein without definition that are
      defined in the Note or in the Mortgage shall have the same meaning herein as
      in
      the Note or in the Mortgage, as the case may be, as herein modified.





B.  
      The Note matured on January 10, 2006, but has not been paid in full. The
      Borrower has continued to make, and the Bank has continued to receive, payments
      on a monthly basis as if the Note had not matured, without the Bank waiving
      or
      modifying said maturity. The Borrower has requested certain modifications to
      the
      Note, including an extension of said Maturity Date of January 10, 2006. The
      Bank
      is willing to agree to such modifications, subject to the terms and conditions
      of this Agreement.





IN
      CONSIDERATION OF the foregoing and the sum of Ten Dollars ($10.00), and for
      other good and valuable consideration, the receipt and sufficiency of which
      are
      hereby acknowledged, the parties hereto do hereby agree as follows:





1. Effective
      as of the date hereof, the Note is hereby amended as follows:





(a) The
      Maturity Date is hereby extended and changed to April 10, 2007. The Borrower
      may
      elect further to extend the Maturity Date to April 10, 2008, by notifying the
      Bank of such election and paying the Bank an extension fee of $36,750.00 on
      or
      before March 10, 2007, provided that (i) prior to the time of such election,
      the
      Bank has not exercised its right to accelerate the maturity of the Note
      following any default, and (ii) at the time of such election, no Event of
      Default then exists and no other event, set of facts or circumstances has then
      occurred and is then continuing which, with the giving of notice or the passage
      of time, or both, would constitute such an Event of Default.





(b)        
      Commencing on the date hereof, the Interest Rate on the Note shall be changed
      to
      a fluctuating rate of interest equal to the from time to time prime rate
      published in The Wall Street Journal (the “Prime Rate”), it being understood
      that if more than one such rate is published, the highest of such rates will
      be
      used. Currently, the Prime Rate is 7.75% per annum. The effective rate of
      interest on the Note shall change on each day that the Prime Rate
      changes.





(c)         
      Payments of principal and interest shall continue to be due monthly in arrears
      on the tenth (10th) day of each calendar month (with the next such payment
      due
      on April 10, 2006) until the Maturity Date (as herein provided) in an amount
      from time to time as determined by the Bank, in its sole discretion (absent
      manifest error), equal to the monthly payment required as of each such payment
      day to amortize the then current outstanding principal balance of the Note
      at
      the then applicable Interest Rate over the then remaining portion of the
      original twenty-year amortization period.




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(d)        
      Each of the following additional events shall constitute an Event of Default
      under the Note:





(o)        
      If the amount of the outstanding principal balance of the Note plus all
      interest, fees, and charges due thereunder or in connection therewith shall
      at
      any time exceed fifty percent (50%) of the value of the Mortgaged Property,
      as
      determined by the Bank in its sole discretion (and such event shall constitute
      an Event of Default notwithstanding the terms of Section 4-27 (a) of the
      Mortgage).





(p)        
      The failure of the Borrower to maintain and hold at all times, in its name,
      cash
      and cash equivalents, free from any and all encumbrances, in an amount not
      less
      than $1,000,000.00 (and such event shall constitute an Event of Default
      notwithstanding the terms of Section 4-27 (c) of the Mortgage).





(q)        
      The failure of the Borrower to maintain at all times a Tangible Net Worth of
      not
      less than $7,000,000.00. “Tangible Net Worth” means the amount equal to the
      Borrower’s stockholders’ equity, minus the sum of its intangible assets
      (patents, goodwill, etc.) and amounts due Borrower from any employee or parent,
      subsidiary or other affiliate of Borrower, all determined in accordance with
      generally accepted accounting principles consistently applied
      (“GAAP”).





2. The
      Borrower shall establish on the date hereof, fund and maintain with the Bank,
      an
      account (the “Debt Service Reserve Account”) in an amount satisfactory to the
      Bank and equal to at least six (6) times the monthly payment due on the Note
      from time to time. Initially, the sum of $211,000.00 shall be maintained in
      the
      Debt Service Reserve Account. If from time to time the Bank determines that
      the
      amount then in the Debt Service Reserve Account is less than six (6) times
      the
      then monthly payment due on the Note, upon notice to the Borrower, the Borrower
      shall be required to deposit into the Debt Service Reserve Account the amount
      of
      such deficiency. The Debt Service Reserve Account shall not constitute a trust
      fund and may be commingled with other monies held by the Bank. The Borrower
      hereby pledges to the Bank and grants to the Bank a security interest in any
      and
      all monies now or hereafter deposited in the Debt Service Reserve Account as
      additional security for the payment of the Note. Upon the occurrence of an
      Event
      of Default, the Bank may apply any sums then present in the Debt Service Reserve
      Account to the payment of the Note in any order in its sole
      discretion.





3. All
      obligations and representations of the Borrower under this Agreement shall
      be
      secured by the Mortgage and the Loan Documents and a default with respect to
      such obligations or representations shall be a default under the Mortgage and
      the Loan Documents.





4. The
      Borrower hereby warrants that all of the representations and warranties
      contained in the Loan Documents are true and correct as of the date hereof
      (except for Borrower's representation with respect to its financial condition,
      which is accurately reflected on Borrower's most recent financial statements
      provided to the Bank) and that no Event of Default has occurred and is
      continuing under the Note or the other Loan Documents or would constitute such
      an Event of Default but for the requirement that notice be given or time elapse
      or both.





5. The
      Borrower hereby agrees to pay all reasonable fees and expenses incurred by
      the
      Bank in connection with the transaction contemplated by this Agreement,
      including reasonable attorneys' fees.





6. The
      Borrower acknowledges and agrees that as of the date of this Agreement, the
      Borrower is indebted to the Bank under the Note, without limitation, for the
      unpaid principal balance of $3,675,000.00, plus accrued interest on the
      principal balance, and, if any, other charges, fees and expenses as provided
      in
      the Note and the other Loan Documents. It is understood and agreed that such
      principal balance reflects a substantial principal paydown made by the Borrower
      recently as a condition of the Bank entering into this Agreement. The Borrower
      expressly acknowledges that the Note, as herein modified, provides for a balloon
      payment upon maturity of sums equal to the unpaid principal and interest due
      under the Note, as modified by this Agreement, and all other costs, expenses
      and
      charges due thereon, and the Bank has no obligation to the Borrower to extend
      or
      renew the Note beyond the Maturity Date herein provided.





7. The
      Borrower acknowledges that the Bank and its representatives, including but
      not
      limited to its officers, employees and any independent contractors, has
      fulfilled all of its obligations to it under the Loan Documents and that the
      amount of principal recited herein together with accrued interest is due and
      owing as of the date of this Agreement. The Borrower represents and warrants
      that it has no defenses, set-offs or counterclaims to the payment of its
      liabilities and obligations to the Bank as set forth in the Loan Documents,
      as
      modified by this Agreement, with respect to any actions, inactions or statements
      of fact arising or existing prior and up to the date of this Agreement, and
      to
      the extent that the Borrower has any defense, set-off or counterclaim, the
      Borrower hereby affirmatively WAIVES any such claim. The Borrower hereby
      releases and forever discharges the Bank and its representatives from any and
      all claims, defenses, actions, causes of action, suits, controversies,
      agreements, provisions and demands in law or in equity which the Borrower ever
      had, now has or now may have against the Bank or its representatives, including,
      but not limited to, claims relating to and arising out of the Loan Documents
      or
      the administration of the Note to date.





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8. The
      Bank
      does not hereby waive any defaults now existing or hereinafter arising under
      the
      Loan Documents or any of its rights and remedies upon the occurrence of any
      Event of Default under the Loan Documents.





9. This
      Agreement and all other documents, instruments, and agreements executed in
      connection herewith represent the entire agreement of the parties hereto and
      incorporate the final results of all discussions and negotiations between the
      undersigned and the Bank, either express or implied, concerning the matters
      included herein and in such other documents, instruments and agreements, any
      custom, usage, or course of dealings to the contrary notwithstanding. No such
      discussions, negotiations, custom, usage, or course of dealings shall limit,
      modify, or otherwise affect the provisions hereof. Any modification, amendment,
      or waiver of any provision of this Agreement or of any provision of any other
      agreement between the undersigned and the Bank must be executed in writing
      by
      the Bank and the party against which/whom enforcement is sought.





10. Each
      of
      the Note and the other Loan Documents are hereby amended to be consistent with
      the terms and provisions of this Agreement. All references in the Note and
      the
      other Loan Documents to each of the others shall be deemed to refer to such
      document(s) as amended by this Agreement





11. Except
      as
      modified and amended by this Agreement, the Note shall remain in full force
      and
      effect as originally written and the same, as so modified, is hereby ratified
      and confirmed.




12. All
      the
      other Loan Documents are hereby ratified and confirmed as if said instruments
      were executed this day in connection with the Note as modified by this
      Agreement.





[here
      ends this page; the next page is the signature page]




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EXECUTED
      as a sealed instrument as of the date first above written.


WAINWRIGHT
              BANK
              & TRUST COMPANY**/s/
              C.
              Norris**
            By:
            **/s/ Darryl
              J. Fess**Witness
              C.
                Norris
            Name:Darryl
                J. Fess
              Title:
                Senior Vice-President


ZOOM
                  TELEPHONICS,
                  INC.**/s/
John
                  Feeney**
                By:
                **/s/ Frank
                  B. Manning**Witness
                  John
                    Feeney
                Frank
                    B. Manning, President
                  duly
                    authorized
 **/s/
John
                Feeney**
              By:
              **/s/ Robert
                Crist**Witness
                John
                  Feeney
              Robert
                  A. Crist, Treasurer
                duly
                  authorized




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