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                                                                     Exhibit 4.3

                                                                  EXECUTION COPY

                         LOGICAL DESIGN SOLUTIONS, INC.

THIS SECURITY HAS BEEN ACQUIRED FOR INVESTMENT AND HAS NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1993 (THE "ACT") OR THE SECURITIES LAWS OF ANY STATE. THIS
SECURITY MAY NOT BE TRANSFERRED BY SALE, ASSIGNMENT, PLEDGE OR OTHERWISE UNLESS
(i) A REGISTRATION STATEMENT FOR THIS SECURITY UNDER THE ACT IS IN EFFECT OR
(ii) THE CORPORATION HAS RECEIVED AN OPINION OF COUNSEL, WHICH OPINION IS
REASONABLY SATISFACTORY TO THE CORPORATION TO THE EFFECT THAT SUCH REGISTRATION
IS NOT REQUIRED UNDER THE ACT OR THE SECURITIES LAWS OF ANY STATE.

                        9% Senior Subordinated Debenture
                               Due March 19, 2002

                                                          Morristown, New Jersey
No. S-1                                                           March 19, 1997

     FOR VALUE RECEIVED, Logical Design Solutions, Inc., a New Jersey
corporation (the "Company"), hereby, promises to pay to Summit Ventures IV,
L.P., or its registered assigns, the sum of Five Million, Thirty-Two Thousand,
Five Hundred Twenty-One Dollars ($5,032,521) on March 19, 2002, together with
interest, computed on the basis of the actual number of days elapsed over a 360-
day year, on the unpaid principal balance hereof until paid in full at the rate
of nine percent (9%) per annum from the date hereof. Interest shall accrue and
compound annually and shall be paid upon each payment or prepayment of
principal.

     Any interest not paid when due and payable shall thereafter be paid on
demand by the holder of this Debenture (as defined below) together with a late
charge of two percent (2%) of the amount of interest payment due.

     All payments of principal (including any prepayments or redemptions) and
interest hereunder shall be made by the Company in lawful money of the United
States of America in immediately available federal funds (or, at the request of
the holder of this Debenture, by certified or bank check or wire transfer) not
later than 2:00 p.m., Boston, Massachusetts, time, on the date each such payment
is due, by crediting an account in the United States as the holder of this
Debenture may designate in writing to the Company before the scheduled payment
date.

     This Debenture is one of a duly authorized issue of Debentures of the
Company designated as its "9% Senior Subordinated Debentures due March 19, 2002"
(herein called the "Debentures"), in the aggregate principal amount of
$5,296,833.71 and issued under a 9% Senior Subordinated Debenture and Warrant
Purchase Agreement, dated as of March 19, 1997 (herein

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called the "Agreement"), among the Company, certain of its shareholders, Summit
Ventures IV, L.P., Summit Investors III, L.P., Paul F. Lozier and Samedan, Inc.,
to which Agreement and all agreements supplemental thereto reference is hereby
made for a statement of the respective rights and duties thereunder of the
Company, and the holders of the Debentures, and the terms upon which the
Debentures are delivered.

     The principal of this Debenture is subject to prepayment under certain
circumstances, together with accrued interest, all as more particularly set,
forth in the Agreement. The Company agrees to make such payments of principal
and interest on the date and in the amount set forth in the Agreement.

     Notwithstanding anything herein contained to the contrary, the indebtedness
evidenced by the Debenture is, to the extent provided in the Agreement,
subordinate and subject in right of payment to the prior payment in full of all
Senior Debt (as defined in the Agreement), and this Debenture is issued subject
to such provisions, and each holder of Debentures, by accepting the same, agrees
to and shall be bound by such provisions and agrees to take such action as may
be necessary or appropriate to effectuate the subordination as provided in the
Agreement.

     In case an Event of Default, as defined in the Agreement, shall have
occurred and be continuing uncured or unwaived, the principal of all of the
Debentures may be in certain circumstances declared, and upon such declaration
shall become, immediately due and payable, in the manner, with the effect and
subject to the conditions provided in the Agreement.

     No reference herein to the Agreement and no provisions of this Debenture or
of the Agreement shall alter or impair the obligation of the Company, which is
absolute and unconditional, to pay the principal of and interest on this
Debenture at the times, places, and rates, and in the coin or currency, herein
prescribed.

     Under certain circumstances more fully set forth in the Agreement, this
Debenture is transferable by the registered owner hereof, in person or by duly
authorized attorney, on the books of the Company to be kept for that purpose,
upon surrender and cancellation of this Debenture, upon presentation of a duly
executed written instrument of transfer satisfactory to the Company and upon the
transferee's written agreement to be bound by the provisions of the Agreement,
and thereupon a new Debenture or Debentures, of the same aggregate principal
amount and in authorized denominations, will be issued to the transferee or
transferees in exchange therefor; and this Debenture, with or without other
Debentures may in like manner be exchanged for one or more new Debentures of
other authorized denominations but of the same aggregate principal amount, all
subject to the terms and conditions set forth in the Agreement. Any such
transfer or exchange shall be without charge by the Company. Transfer tax or the
like (if any) shall be paid by the holder hereof or the Transferee.

     All terms used in this Debenture which are not defined herein and are
defined in the Agreement shall have the meanings assigned to them in the
Agreement.

     This Debenture shall be deemed to be a contract made under the laws of the
Commonwealth of Massachusetts and shall for all purposes be construed in
accordance with the laws of said Commonwealth.

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     IN WITNESS WHEREOF, the Company has caused this Debenture to be duly
executed as a sealed instrument.

                                          LOGICAL DESIGN SOLUTIONS, INC.


                                          By: /s/  Mary Kay Brooks
                                             ----------------------
Attest:  /s/  E. Bruce Lovenberg             Name:  Mary Kay Brooks
       -------------------------             Title:  President



161611-1

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