<PAGE>   1


                                                                    Exhibit 10.7


                                    PERSHING


                                MARGIN AGREEMENT


To: Pershing, Division of Donaldson, Lufkin & Jenrette Securities Corporation:

In consideration of your accepting and carrying for the undersigned one or more
accounts introduced to you by my broker, bank or other introducing firm
("Introducing Firm"), the undersigned agrees as follows:

ROLE OF PERSHING
1. You are carrying the accounts of the undersigned as clearing broker pursuant
to a cleaning agreement with introducing Firm.  Until receipt from the
undersigned of written notice to the contrary, you may accept from Introducing
Firm, without inquiry or investigation, (i) orders for the purchase or sale of
securities and other property on margin or otherwise, and (ii) any other
instructions concerning said accounts.  Notices to the undersigned concerning
margin requirements or other matters related to the undersigned's accounts
usually will go through undersigned's Introducing Firm although direct notice
to the undersigned with duplicate notice to undersigned's introducing Firm may
occur if market conditions, time constraints or other circumstances require it.
You shall not be responsible or liable for any acts or omissions of
Introducing Firm or its employees.  I understand that Pershing provides no
investment advice nor do you give advice or offer any opinion with respect to
the suitability of any transaction or order.  I understand that my Introducing
Firm is not acting as the agent of Pershing and I agree that I will in no way
hold Pershing, Donaldson, Lufkin & Jenrette Securities Corporation, its other
Divisions, and its Officers, Directors and Agents liable for any trading losses
incurred by me.

APPLICABLE RULES AND REGULATIONS
2. All transactions for the undersigned shall be subject to the constitution,
rules, regulations, customs and usages of the exchange or market and its
clearing house, if any, where executed by you or your agents, including your
subsidiaries and affiliates.

DEFINITIONS
3. For purposes of this agreement "securities, commodities and other property,"
as used herein shall include, but not be limited to money, securities, and
commodities of every kind and nature and all contracts and options relating
thereto, whether for present or future delivery.

LIEN
4. All securities, commodities and other property of the undersigned which you
may at any time be carrying for the undersigned, or which may at any time be in
your possession or under your control, shall be subject to a general lien and
security interest in your favor for the discharge of all the undersigned's
indebtedness and other obligations to you, without regard to your having 

<PAGE>   2

made any advances in connection with such securities and other property and
without regard to the number of accounts the undersigned may have with you.  In
enforcing your lien, you shall have the discretion to determine when securities
and property are to be sold and which contracts are to be closed.
        
LIQUIDATION
5. If, in your discretion you consider it necessary for your protection to
require additional collateral or in the event that a petition in bankruptcy, or
for an appointment of a receive is filed by or against the undersigned, or an
attachment is levied against the accounts of the undersigned, or in the event
of the death of the undersigned, you shall have the right to sell any or all
securities, commodities and other property in the accounts of the undersigned
with you, whether carried individually or jointly with others, to buy any or
all securities, commodities and other property which may be short in such
accounts, to cancel any open orders and to close any or all outstanding
contracts, all without demand for margin or additional margin, notice of sale
or purchase or other notice or advertisement.  Any such sales or purchases may
be made at your discretion on any exchange or other market where such business
is usually transacted, or at public auction or private sale, and you may be the
purchasers for your own account.  It being understood that a prior demand, or
call, or prior notice of the time and place of such sale or purchase shall not
be considered a waiver of your right to sell or buy without demand or notice.

PAYMENT OF INDEBTEDNESS UPON DEMAND AND LIABILITY FOR COSTS OF COLLECTION
6. The undersigned shall at all times be liable for the payment upon demand of
any debit balance or other obligations owing in any of the accounts of the
undersigned with you and the undersigned shall e liable to you for any
deficiency remaining in any such accounts in the event of the liquidation
thereof, in whole or in part, by you or by the undersigned; and, the
undersigned shall make payments of such obligations and indebtedness upon
demand.  The reasonable costs and expense of collection of the debit balance,
recovery of securities, and any unpaid deficiency in the accounts of the
undersigned with you, including, but not limited to, attorney's fees, incurred
and payable or paid by you shall be payable to you by the undersigned.

PLEDGE OF SECURITIES
7. All securities, commodities and other property now or hereafter held,
carried or maintained by you in your possession in any of the accounts of the
undersigned may be pledged and repledged by you from time to time, without
notice to the undersigned, either separately or in common with other such
securities, commodities and other property for any amount due in the accounts
of the undersigned, or for any greater amount, and you may do so without
retaining to your possession or control for delivery a like amount of similar
securities, commodities or their property.

MARGIN REQUIREMENTS, CREDIT CHARGES AND CREDIT INVESTIGATION
8. The undersigned will at all times maintain such securities, commodities and
other property in the accounts of the undersigned for margin purposes as you
shall require from time to time and the monthly debit balances or adjusted
balances in the accounts of the undersigned with you shall be charged, in
accordance with your practice, with interest at a rate permitted by the laws of
the 



                                     - 2 -
<PAGE>   3

State of New York.  It is understood that the interest charge made to the
undersigned's account at the close of a charge period will be added to the
opening balance for the next charge period unless paid.

     I acknowledge receipt from my introducing Firm of the disclosure statement
which explains the conditions under which interest can be charged to my
account, the annual rate of interest, how debit balances are determined and the
methods of computing interest.

     You may exchange credit information about the undersigned with others.
You may request a credit report on the undersigned and upon request, you will
state the name and address of the consumer reporting agency that furnished it.
If you extend, update or renew the undersigned's credit, you may request a new
credit report without telling the undersigned.

COMMUNICATIONS
9. Communications may be sent to the undersigned at the current address of the
undersigned, which is on file at your office, or at such other address as the
undersigned may hereafter give you in writing, or through my Introducing Firm,
and all communications, so sent, whether by mail, telegraph, messenger or
otherwise, shall be deemed given to the undersigned personally, whether
actually received or not.

SCOPE AND TRANSFERABILITY
10. This agreement shall cover individually and collectively all accounts which
the undersigned may open or reopen with you, and shall inure to the benefit of
their successors whether by merger, consolidation or otherwise, and assigns,
and you may transfer the accounts of the undersigned to your successors and
assigns, and this agreement shall be binding upon the heirs, executors,
administrators, successors and assigns of the undersigned.

NON-INVESTMENT ADVICE
11. The undersigned acknowledges that you will not provide the undersigned with
any legal, tax or accounting advice, that your employees are not authorized to
give any such advice and that the undersigned will not solicit or rely upon any
such advice from you or your employees whether in connection with transactions
in or for any of the accounts of the undersigned or otherwise.  In making
legal, tax or accounting decisions with respect to transactions in or for the
accounts of the undersigned or any other matter, the undersigned will consult
with an rely upon its own advisors and not you, and you shall have no liability
therefor.

EXTRAORDINARY EVENTS
12. You shall not be liable for loss caused directly or indirectly by
government restrictions, exchange or market rulings, suspension of trading,
ware, strikes or other conditions beyond your control.

REPRESENTATIONS AS TO CAPACITY TO ENTER INTO AGREEMENT
13. The undersigned, if an individual, represents that the undersigned is of
full age, that unless otherwise disclosed to you in writing, the undersigned is
not an employee of any exchange, or of 


                                     - 3 -
<PAGE>   4
   
any corporation of which any exchange owns a majority of the capital stock, or
of a member firm or member corporation registered on any exchange or of a bank,
trust company, insurance company, or of any corporations, firm or individual
engaged in the business of dealing either as broker or as principal in
securities, bills of exchange, acceptances or other forms of commercial paper.
The undersigned further represents that no one except the undersigned has an
interest in the account or accounts of the undersigned with you.

JOINT AND SEVERAL LIABILITY
14. If the undersigned shall consist of more than one individual, their
obligations under this agreement shall be joint and several.  The undersigned
have executed the Joint Account Agreement and made the election required
therein.

OPTION TRANSACTIONS
15. If at any time the undersigned shall enter into any transaction for the
purchase or sale of an option contract, the undersigned hereby agrees to first
obtain from the Introducing Firm the then current disclosure statements of the
Options Clearing Corporation and further agrees to abide by the rules of any
national securities association, registered securities exchange or clearing
organization applicable to the trading of option contracts and, acting alone or
in concert, will not violate the position or exercise limitation rules of any
such association or exchange or of the Options Clearing Corporation or other
clearing organization.

SEPARABILITY
16. If any provision or condition of this agreement shall be held to be invalid
or unenforceable by any court, or regulatory or self-regulatory agency or body,
such invalidity or unenforceability shall attach only to such provision or
condition.  The validity of the remaining provisions and conditions shall not
be affected thereby and this agreement shall be carried out as if any such
invalid or unenforceable provision or condition were not contained herein.

HEADINGS ARE DESCRIPTIVE
17. The heading of each provision hereof is for descriptive purposes only and
shall not be deemed to modify or qualify any of the rights or obligations set
forth in each such provision.

ASSIGNMENT OF PERSHING'S RIGHTS UNDER THIS AGREEMENT TO INTRODUCING FIRM
18. The undersigned agrees that any rights that Pershing has under this
agreement, including but not limited to the right, to collect any debit balance
or other obligations owing in any of the accounts of the undersigned may be
assigned to the Introducing Firm of the undersigned so that the undersigned's
Introducing Firm may collect from the undersigned independently or joined with
Pershing or enforce any other rights granted to Pershing under this agreement.


ARBITRATION DISCLOSURES
19.  -   ARBITRATION IS FINAL AND BINDING ON THE PARTIES.



                                     - 4 -

<PAGE>   5



       -   PRE-ARBITRATION DISCOVERY IS GENERALLY MORE LIMITED THAN AND
           DIFFERENT FROM COURT PROCEEDINGS.

       -   THE ARBITRATORS' AWARD IS NOT REQUIRED TO INCLUDE FACTUAL
           FINDINGS OR LEGAL REASONING AND ANY PARTY'S RIGHT TO APPEAL OR TO
           SEEK MODIFICATION OF RULINGS BY THE ARBITRATORS IS STRICTLY LIMITED.

       -   THE PANEL OF ARBITRATORS WILL TYPICALLY INCLUDE A MINORITY OF
           ARBITRATORS WHO WERE OR ARE AFFILIATED WITH THE SECURITIES INDUSTRY.

AGREEMENT TO ARBITRATE CONTROVERSIES
20. IT IS AGREED THAT ANY CONTROVERSY BETWEEN OR AMONG THE UNDERSIGNED,
PERSHING AND INTRODUCING FIRM OR ANY OF THEM ARISING OUT OF PERSHING'S OR
INTRODUCING FIRM'S BUSINESS OR THIS AGREEMENT, SHALL BE SUBMITTED TO
ARBITRATION BEFORE THE NEW YORK STOCK EXCHANGE, INC. OR ANY OTHER NATIONAL
SECURITIES EXCHANGE ON WHICH A TRANSACTION GIVING RISE TO THE CLAIM TOOK PLACE
(AND ONLY BEFORE SUCH EXCHANGE) OR THE NATIONAL ASSOCIATION OF SECURITIES
DEALERS, INC., AS THE UNDERSIGNED MAY ELECT AND IN ACCORDANCE WITH THE RULES
OBTAINING OF THE SELECTED ORGANIZATION.  ARBITRATION MUST BE COMMENCED BY
SERVICE UPON THE OTHER PARTY OF A WRITTEN DEMAND FOR ARBITRATION OR A WRITTEN
NOTICE OF INTENTION TO ARBITRATE, THEREIN ELECTING THE ARBITRATION TRIBUNAL.
IN THE EVENT THE UNDERSIGNED DOES NOT MAKE SUCH ELECTION WITHIN FIVE (5) DAYS
OF SUCH DEMAND OR NOTICE, THEN THE UNDERSIGNED AUTHORIZES YOU TO DO SO ON
BEHALF OF THE UNDERSIGNED.

NO PERSON SHALL BRING A PUTATIVE OR CERTIFIED CLASS ACTION TO ARBITRATION, NOR
SEEK TO ENFORCE ANY PRE-DISPUTE ARBITRATION AGREEMENT AGAINST ANY PERSON WHO
HAS INITIATED IN COURT A PUTATIVE CLASS ACTION; AND WHO IS A MEMBER OF A
PUTATIVE CLASS AND WHO HAS NOT OPTED OUT OF THE CLASS WITH RESPECT TO ANY
CLAIMS ENCOMPASSED BY THE PUTATIVE CLASS ACTION UNTIL: (I) THE CLASS
CERTIFICATION IS DENIED; (II) THE CLASS IS DECERTIFIED; OR (III) THE CUSTOMER
IS EXCLUDED WAIVER OF ANY RIGHTS UNDER THIS AGREEMENT EXCEPT TO THE EXTENT
STATED HEREIN.

THE LAWS OF THE STATE OF NEW YORK GOVERN
21. THIS AGREEMENT AND ITS ENFORCEMENT SHALL BE GOVERNED BY THE LAWS OF THE
STATE OF NEW YORK.

LOAN CONSENT

                                     - 5 -

<PAGE>   6

22. BY SIGNING THIS AGREEMENT, THE UNDERSIGNED ACKNOWLEDGES THAT SECURITIES NOT
FULLY PAID FOR BY THE UNDERSIGNED MAY BE LOANED TO YOU OR LOANED OUT TO OTHERS.

THIS AGREEMENT CONTAINS A PRE-DISPUTE ARBITRATION CLAUSE IN PARAGRAPH 20 ON
THIS PAGE.  I ACKNOWLEDGE RECEIVING A COPY OF THIS AGREEMENT.


                                   SIGNATURES



(If a Corporation, Partnership or Other Entity)        (If Individual)

GUARDIAN TECHNOLOGIES INTERNATIONAL, 
INC.
------------------------------------------     -------------------------------
        (Name of Entity)
                                               -------------------------------
                                               (Second Party if Joint Account)

By     /s/ Oliver L. North
    --------------------------------------

Title     President
      ------------------------------------

DATED      24 June 1996                              ACCOUNT NO.
      --------------------------------------------              ----------------
                                                    






                                     - 6 -