Executed in 6 Parts
                                                             Counterpart No. ( )


                              NATIONAL EQUITY TRUST

                          LOW FIVE PORTFOLIO SERIES 217

                            REFERENCE TRUST AGREEMENT


     This Reference  Trust Agreement  dated , 2000 among  Prudential  Securities
Incorporated,  as Depositor and The Chase Manhattan Bank, as Trustee, sets forth
certain provisions in full and incorporates other provisions by reference to the
document  entitled  "National  Equity  Trust Low Five  Portfolio  Series,  Trust
Indenture and  Agreement"  (the "Basic  Agreement")  dated April 25, 1995.  Such
provisions  as  are  set  forth  in  full  herein  and  such  provisions  as are
incorporated by reference constitute a single instrument (the "Indenture").

                                WITNESSETH THAT:


     In  consideration  of the  premises  and of the  mutual  agreements  herein
contained, the Depositor and the Trustee agree as follows:


                                     Part I.

                     STANDARD TERMS AND CONDITIONS OF TRUST


     Subject to the provisions of Part II hereof,  all the provisions  contained
in the Basic  Agreement are herein  incorporated  by reference in their entirety
and  shall be deemed  to be a part of this  instrument  as fully and to the same
extent as though said  provisions had been set forth in full in this  instrument
except that the Basic Agreement is hereby amended in the following manner:

A.   Article  I,  entitled  "Definitions",  paragraph  22,  shall be  amended as
     follows:

               "Trustee shall mean the Chase Manhattan Bank, or any successor
               trustee appointed as hereinafter provided."





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B.   Article II, entitled "Deposit of Securities; Acceptance of Trust", shall be
     amended as follows:

               The second sentence of Section 2.03 Issue of Units shall be
               amended by deleting the words "on any day on which the Depositor
               is the only Unit Holder".


C.   Article  III,  entitled  "Administration  of  Trust",  shall be  amended as
     follows:

          (i)  Section 3.01 Initial Costs shall be amended to substitute the
               following language:

               Section 3.01. Initial Cost The costs of organizing the Trust and
               sale of the Trust Units shall, to the extent of the expenses
               reimbursable to the Depositor provided below, be borne by the
               Unit Holders, provided, however, that, to the extent all of such
               costs are not borne by Unit Holders, the amount of such costs not
               borne by Unit Holders shall be borne by the Depositor and,
               provided further, however, that the liability on the part of the
               Depositor under this section shall not include any fees or other
               expenses incurred in connection with the administration of the
               Trust subsequent to the deposit referred to in Section 2.01. Upon
               notification from the Depositor that the primary offering period
               is concluded, the Trustee shall withdraw from the Account or
               Accounts specified in the Prospectus or, if no Account is therein
               specified, from the Principal Account, and pay to the Depositor
               the Depositor's reimbursable expenses of organizing the Trust and
               sale of the Trust Units in an amount certified to the Trustee by
               the Depositor. If the balance of the Principal Account is
               insufficient to make such withdrawal, the Trustee shall, as
               directed by the Depositor, sell Securities identified by the
               Depositor, or distribute to the Depositor Securities having a
               value, as determined under Section 4.01 as of the date of
               distribution, sufficient for such reimbursement. The
               reimbursement provided for in this section shall be for the
               account of the Unitholders of record at the conclusion of the
               primary offering period and shall not be reflected in the
               computation of the Unit Value prior thereto. As used herein, the


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               Depositor's reimbursable expenses of organizing the Trust and
               sale of the Trust Units shall include the cost of the initial
               preparation and typesetting of the registration statement,
               prospectuses (including preliminary prospectuses), the indenture,
               and other documents relating to the Trust, SEC and state blue sky
               registration fees, the cost of the initial valuation of the
               portfolio and audit of the Trust, the initial fees and expenses
               of the Trustee, and legal and other out-of-pocket expenses
               related thereto, but not including the expenses incurred in the
               printing of preliminary prospectuses and prospectuses, expenses
               incurred in the preparation and printing of brochures and other
               advertising materials and any other selling expenses. Any cash
               which the Depositor has identified as to be used for
               reimbursement of expenses pursuant to this Section shall be
               reserved by the Trustee for such purpose and shall not be subject
               to distribution or, unless the Depositor otherwise directs, used
               for payment of redemptions in excess of the per-Unit amount
               allocable to Units tendered for redemption. As directed by the
               Depositor, the Trustee will advance funds to the Trust in an
               amount necessary to reimburse the Depositor pursuant to this
               Section and shall recover such advance from the sale or sales of
               Securities at such time as the Depositor shall direct, but in no
               event later than the termination of the Trust. Repayment of any
               such advance shall be secured by a lien on the assets of the
               Trust prior to the interest of the Unit Holders as provided in
               Section 6.04.

          (ii) The third paragraph of Section 3.05 Distribution shall be amended
               to add the following sentence at the end thereof:

               "The Trustee shall make a special distribution of the cash
               balance in the Income and Principal accounts available for such
               distribution to Unit Holders of record on such dates as the
               Depositor shall direct, provided however, that no such
               distribution shall be made if the assets of the Trust subsequent
               to such distribution would not exceed any Deferred Sales Charge
               payable and other trust expenses."

          (iii) The second to the last paragraph of Section 3.08 Sale of
               Securities shall be amended to replace the word "equal" with the
               following phrase: "be sufficient to pay."


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D.   Reference  to United  States  Trust  Company of New York in its capacity as
     Trustee  is  replaced  by the Chase  Manhattan  Bank  throughout  the Basic
     Agreement.

E.   Section 6.05 shall be amended to delete the clause "if the Depositor  shall
     determine  in good  faith that  there has  occurrred  either (1) a material
     deterioration  in the  creditworthiness  of the  Trustee or (2) one or more
     negligent  acts on the  part of the  Trustee  having a  materially  adverse
     effect,  either singly or in the aggregate,  on the Trust or on one or more
     Trusts, such that the replacement of the Trustee is in the best interest of
     the Unit Holders" and insert in place thereof  "upon the  determination  of
     the Depositor to remove the Trustee for any reason,  either with or without
     cause,  including but not limited to a determination  by the Depositor that
     the  Trustee  has  materially  failed to  perform  its  duties  under  this
     Indenture and the interest of Unit Holders has been substantially  impaired
     as a result".
                                       Part II.

                         SPECIAL TERMS AND CONDITIONS OF TRUST


     The following special terms and conditions are hereby agreed to:

                  A.    The Trust is denominated National Equity
            Trust, Low Five Portfolio Series 217.

                  B.    The Units of the Trust shall be subject to
            a deferred sales charge.

                  C. The contracts for the purchase of common stock listed in
            Schedule A hereto are those which, subject to the terms of this
            Indenture, have been or are to be deposited in Trust under this
            Indenture as of the date hereof.

                  D.    The term "Depositor" shall mean Prudential
            Securities Incorporated.

                  E.    The aggregate number of Units referred to
            in Sections 2.03 and 9.01 of the Basic Agreement is
                     as of the date hereof.

                  F.    A Unit of the Trust is hereby declared
            initially equal to 1/     th of the Trust.

                  G.    The term "First Settlement Date" shall mean
                     , 2000.

                  H.    The terms "Computation Day" and "Record
            Date" shall mean on the tenth day of        2000,        2000,
            2001, and       2001.

                  I.    The term "Distribution Date" shall mean on the twenty-
            fifth day of        2000,        2000,        2001, and      2001
            or as soon thereafter as possible.

                  J.    The term "Termination Date" shall mean
                     , 2001.

                  K. The Trustee's Annual Fee shall be $ (per 1,000 Units) for
            100,000,000 and above units outstanding; $0.80 (per 1,000 Units) for
            50,000,000 - 99,999,999 units outstanding; $0.86 (per 1,000 Units)
            for 49,999,999 and below units outstanding. In calculating the
            Trustee's annual fee, the fee applicable to the number of units
            outstanding shall apply to all units outstanding.



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                  L.    The Depositor's Portfolio supervisory
            service fee shall be $0.25 per 1,000 Units.

                  [Signatures and acknowledgments on separate pages]