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                                                                   Exhibit 10.25


                                 PROMISSORY NOTE

$300,000                                                          AUGUST 9, 2001

     FOR VALUE RECEIVED, CAPSULE COMMUNICATIONS, INC. with principal offices
located at 2 Greenwood Square, 3331 Street Road, Suite 275, Bensalem,
Pennsylvania 19020 hereafter referred to as the "Borrower") promises to pay to
the order of Covista, Inc. (the "Lender") at its principal office, 150 Clove
Road, Little Falls, New Jersey 07424, the sum of Three Hundred Thousand and
00/100 ($300,000) Dollars (the "Principal") with interest thereon as more fully
set forth below.

     This Note shall bear interest from the date hereof and during the term
hereof at a rate of eight and three-quarter (8 3/4) percent per annum. Interest
and Principal shall be payable in full one year from the date above written (the
"Due Date").

     Occurrence of any one of the following events shall be deemed to be a
default under the terms of this Note:

     1.   Failure to pay accrued Interest or the Principal of this Note; or

     2.   Borrower shall make an assignment for the benefit of creditors or
          attempt to effect a composition or arrangement with creditors or be
          adjudged bankrupt or insolvent or any receiver, trustee, liquidator,
          conservator or like officer be appointed to take custody, possession
          or control of any property of Borrower; or Borrower shall file any
          petition, answer of other pleading in any proceeding under any
          Bankruptcy Act as now or hereafter in effect for the purpose of
          affording relief to debtors from their obligations. However, with
          respect to any event of default, as set forth in this subsection 2, no
          default shall be deemed to have occurred unless Borrower fails to cure
          such default within thirty (30) days after the occurrence thereof; or

     3.   Upon failure by Borrower to make payment on this Note at its stated
          due date, or if a default (as defined above) shall have occurred, the
          Lender may, in addition to such other and further rights and remedies
          provided by law, collect interest from the date of such maturity on
          the principal balance owing hereon at the rate of interest of five
          (5%) percent per annum in excess of that specified in this Note, but
          not in excess of the highest legal rate permitted in the State of New
          Jersey.

     This Note shall also become immediately due and payable in full on not less
than five (5) days prior written notice to Borrower if a certain proposed merger
between Borrower and Lender's subsidiary is not consummated on or prior to
December 31, 2001, or any merger agreement between said parties is terminated
prior to said date, whichever is sooner.

     If this Note is referred to an attorney for collection, regardless of
whether such attorney is an employee of the Lender, Borrower agrees that Lender
shall be entitled to collect reasonable attorney's fees and expenses for the
cost of such collection.

     This Note may be prepaid in whole or in part without penalty or premium;
however, any prepayment of less than the full principal balance hereof shall be
in the inverse order of maturity.

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     This Note shall be payable when due without defense, other than full and
legal payment, offset, deduction or claim of any kind whatsoever.

     The obligations evidenced by this Note are binding upon the Borrower, its
successors and/or assigns.

     Presentment for payment, notice of dishonor, and notice of protest are
hereby waived by the makers, and any guarantor or and endorser hereof.

     IN WITNESS WHEREOF, the undersigned has caused this Note to be executed as
of the date and year first above written.

      ATTEST:                            CAPSULE COMMUNICATIONS, INC.

      /s/ Randolph A. Fry                /s/ David B. Hurwitz
      ---------------------------        -------------------------------------
                                         By: David Hurwitz
                                         Title: President & CEO

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