LEASE AGREEMENT

     THIS LEASE AGREEMENT (the "Lease"), made as of the first day of June, 
1991 by and between Botzler-Emery Associates Guilford Ten Limited 
Partnership, a Maryland partnership ("Landlord") and BATS, Inc., a Maryland 
corporation ("Tenant").
 
                                 WITNESSETH

1.  DEMISED PREMISES:  In consideration of the rent hereinafter reserved and 
of the covenants hereinafter contained, Landlord hereby leases to Tenant, 
and Tenant hereby leases from Landlord, the space described on Exhibit A 
generally known as 9570 Berger Road, Columbia, Maryland, attached hereto, 
containing 65,923 square feet, more or less, which space is hereinafter 
referred to as the "Premises."

2.  TERM:  This Lease shall be for a term of ten (10) years, commencing on 
the first day of June, 1991, and ending on the last day of May, 2001 both 
dates inclusive, (the "Term") unless the Lease is sooner terminated or 
extended, provided, however, that if Landlord is unable to deliver possession 
of the Premises in substantially habitable condition on June 1, 1991, the 
Term shall be adjusted to commence with the delivery of possession of the 
Premises. In the event the Tenant shall take possession of the Premises on 
any day other than the first day of any calendar month, the Tenant shall pay 
PRO RATA rent until the end of that calendar month and the  Term of this 
Lease shall commence on the first day of the following month. 

3.  OPTION TO RENEW AND EXTENSION:  The term of years herein reserved may, at 
Tenants option, be renewed and extended for two (2) successive terms of five 
(5) years each for the same rent and subject to all terms, conditions and 
covenants applicable to the Term. Tenant shall give notice of its exercise of 
such option to renew and extend not later than one hundred eighty (180) days 
prior to the end of such term and, in the event Tenant shall fail to give 
such notice, the parties agree that it shall be conclusively deemed and 
presumed that Tenant has affirmatively exercised the option to renew and 
extend.

4.  MINIMUM RENT:  During the term hereof Tenant agrees to pay a minimum 
annual rent of three hundred and seventy five thousand dollars ($375,000), 
payable without diminution, counterclaim, deduction, set-off, or demand, in 
equal monthly installments of thirty one thousand, two hundred and fifty 
dollars ($31,250), the first installment payable upon commencement of the 
Term of this Lease and the remaining installments payable in advance on the 
first day of each calendar month during the Term. All rent and other payments 
due from Tenant to Landlord shall be paid to the Landlord at 9570 Berger Road, 
Columbia, MD 21046 during regular

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business hours. If any installment of rent accruing hereunder or any other 
sums payable hereunder shall not be paid with five (5) days after the due 
date, the rental and such other sums due shall, without affecting any of 
Landlord's other rights under this Lease, be increased by a late charge of 
5%, or $75.00 whichever is greater, per month until paid, time being of the 
essence of this Lease. No payment by Tenant or receipt by Landlord of a 
lesser amount than the monthly installment of the rent stipulated shall be 
deemed to be other than on account of the stipulated rent, nor shall any 
endorsement or statement on any check or any letter accompanying any check or 
payment as rent be deemed an accord and satisfaction, and Landlord may accept 
such check for payment without prejudice to Landlord's right to recover the 
balance of such rent or pursue any other remedy provided in this Lease.

     It is the intention of the parties to this Lease Agreement that the 
initial annual Minimum rent applicable to the premises shall be computed by 
multiplying the total number of square feet within the gross building area by 
$5.50, which sum shall be the initial Minimum Rent. 

5.  DEFINITIONS:  The following definitions shall apply to the terms used in 
this Lease:

    A.  The term "Tax Year" means the period from July 1 of any calendar year 
        through June 30 of the next calendar year, unless a different tax 
        year is adopted for Real Estate Taxes by any taxing authority, in 
        which event the term "Tax Year" shall mean the tax year so adopted.

    B.  The term "Building" means the structure on the Premises for use and 
        occupancy by the Tenant.

    C.  The term "Lease Year" shall mean the successive 12-month periods 
        during the term of the lease, each period commencing on the first day 
        of the calendar month in which the term commencement date of this 
        Lease falls.

    D.  The term "Minimum Rent" means the rental set forth in Paragraph 4 of 
        the Lease, as adjusted from time to time in accordance with Paragraph 6
        below.

6.  RENT ADJUSTMENT:  Effective each and every Lease Year after the first 
Lease Year, the monthly Minimum Rent shall be increased by the rate of three 
percent (3%) of the Minimum Rent paid by the tenant during the year preceding 
each annual increase. For example, if the Minimum Rent for the preceding 
Lease Year was $1,000 than the Minimum Rent for the current Lease Year shall 
be increased to $1,030.00, the following year would be $1,060.90.

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7.  TAXES, UTILITIES AND INSURANCE:  (a ) In addition to and not in lieu of 
all or any portion of the Minimum Rent, the Tenant shall pay as additional 
rent all State, County, City and other AD VALOREM real estate taxes, together 
with any sewer and water rent charges, including, without limitation, front 
foot benefit charges or metropolitan sanitary district charges from the date 
upon which the Landlord delivers possession to the Tenant. The Tenant shall 
deliver a copy of a receipted tax bill to Landlord on or before September 30 
of each year.

     (b) Tenant shall pay all charges for gas, electricity, light, heat, all 
public charges for sanitary sewage discharged from the Premises and for water 
consumed on the Premises, power and all other utilities and telephone or 
other communication services used, rendered or supplied upon or in connection 
with the Premises.

     (c) Tenant shall keep the Improvements insured throughout the term of 
this Lease, and any renewal term, against loss or damage by fire and such 
other risks as may be included in a special Multi-Peril Hazard Insurance 
Policy providing coverage in an amount at least equal to the full insurable 
replacement value of the Improvements. Such insurance shall be effected under 
an enforceable policy naming Landlord and any mortgagee as insured, as their 
respective interests may appear, issued by an insurer acceptable to Landlord 
and its mortgagee, licensed in the state where the policy is issued and where 
the property is located. The original of such policy shall be delivered to 
Landlord. Said policy shall contain an agreed amount clause and a waiver of 
subrogation clause and shall not contain any co-insurance provision. The 
policy must provide for 100% of the cost of replacement in the event of a 
claim. In the event of a mortgage on the Premises, the policy shall contain 
the standard mortgagee clause in favor of the mortgagee. Within 15 days after 
the premium on the policy shall be due and payable, the Landlord and its 
mortgagee(s) shall be furnished with satisfactory evidence of its payment. 
Said policy shall provide that cancellation shall not be made without 30 days 
written notice to Landlord and its mortgagee.

8.  SECURITY DEPOSITS:  Landlord will not require a Security Deposit of 
Tenant.

9.  REPAIRS:  The Tenant agrees to maintain the premises in good repair 
during the term of this Lease, at its own expense, including, without 
limitation, the floors, walls, ceiling, interior or exterior doors, inside 
plumbing, all heating, ventilating, and other equipment and fixtures installed 
by the Landlord. Tenant agrees that it will at its own expense maintain and 
replace when necessary all equipment, including but not limited, to doors 
and/or door closures, fixtures, windows and floor coverings and that it will 
redecorate the Premises when necessary. Tenant agrees that it will have done 
at its own expense any work at the Premises resulting from Tenant's 
occupancy which may be required by law or regulation or lawful

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authority. Landlord agrees within a reasonable time after receipt of 
written notice from the Tenant to make all capital repairs reasonably 
necessary to the structural portion of the Premises and roof subject to 
Paragraph 13 hereof. The Tenant also agrees, at its own expense to repair any 
damage caused by the operation of its business or by the actions of its 
employees, agents or invitees on or about the Premises, the Building, Land or 
the common areas and facilities, including, without limitation, any damage to 
the parking areas caused by the operation (including, without limitation, the 
driving, loading or unloading) of delivery vans, trash, carts or vehicles of 
any sort servicing Tenant's business or the Premises.

10.  USE OF PREMISES:  Tenant covenants to use the Premises only for offices 
and production areas for carrying on the business of developing and 
manufacturing aircraft equipment and other lawful purposes and to permit 
Landlord to transmit heat, air conditioning and electric current through 
the Premises at all times at the discretion of Landlord, provided, however, 
that Landlord shall not exercise this right in such a way as to unreasonably 
inconvenience Tenant or intefere with Tenant's use of Premises.

11. TENANT'S AGREEMENTS:  Tenant covenants and agrees:

     A.  To pay to Landlord the Minimum rent, additional and other rent 
         amounts during the Term and until possession of the premises is 
         redelivered to Landlord free and clear of debris.

     B.  To save Landlord harmless and indemnified from all loss, damage, 
         liability or expense incurred, suffered or claimed by any person by 
         reason of Tenant's neglect or use of the Premises, Land or Building 
         or of anything therein, or of water, steam, electricity or other 
         utility; or by reason of any injury, loss or damage to any person or 
         property upon the Premises not caused by the gross negligence of 
         Landlord and to be answerable for all nuisances caused or suffered 
         on the Premises, or caused by Tenant in the Building, Land or common 
         areas and facilities or on the approaches thereto.

     C.  Not to strip or overload, damage or deface the Premises or 
         hallways, stairways, elevator, common areas and facilities or other 
         approaches thereto, of the Building, or fixtures therein or used 
         therewith, nor to permit any hole to be made in any of the same.

     D.  Not to suffer or permit any trade or occupation to be carried on or use
         made of the Premises which shall be unlawful, noisy, offensive or 
         injurious to any person or property, or such as to increase the 
         danger of fire or affect or make void or voidable any insurance on 
         the Building, or which may render any increased or extra premium 
         payable for such insurance, or which shall be 

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         contrary to any law or ordinance, rule or regulation, from time to 
         time established by any public authority. Tenant expressly agrees to 
         conform to all rules and regulations from time to time established 
         by the Insurance Rating Bureau of the Jurisdiction in which the 
         Premises are located.

     E.  Not to place upon the interior or exterior of the Building or any 
         window or any part thereof or door of the Premises any placard, 
         sign, lettering, window covering or drapes, except such and in such 
         place and manner as shall have been first approved in writing by 
         Landlord; to have installed at Tenant's expense a building standard 
         sign, as determined by Landlord, for the entrance door to the 
         Premises; and not to use any floor adhesive in the installation of 
         any carpeting.

     F.  That all automobile parking areas, driveways and other facilities 
         furnished by Landlord including employee parking areas, pedestrian 
         sidewalks and ramps, landscaped areas, exterior stairways and other 
         common areas, facilities and improvements provided by Landlord for 
         the general use in common of tenants, their agents, employees, 
         invitees and customers shall at all times be subject to the 
         exclusive control and managment of Landlord.

     G.  Except upon written permission from Landlord, Tenant shall not, by 
         its agents, servants, employees, clients or invitees occupy a number 
         of parking spaces greater than two (2) for each 2000 square feet of 
         the Premises.

12.  LANDLORD'S RIGHT OF ACCESS: Landlord shall have the right to enter the 
Premises during usual business hours for the purpose of inspecting or making 
repairs to the Premises or Building. If the repairs necessitate the cutting 
of any carpeting belonging to Tenant, Landlord shall have no obligation to 
replace said carpeting but shall repair same. Landlord shall have the right 
to show the Premises to prospective tenants during the last six (6) months of 
the Lease term.

13.  ALTERATIONS:  Tenant will not without the prior written consent of 
Landlord paint the exterior of the Premises or make or permit anyone to make 
any alterations in or additions to the exterior of the Premises, nor will 
Tenant install any equipment or any kind that will require any alterations or 
additions to or the use of the water system, heating system, plumbing system, 
air conditioning system or electrical system, nor will Tenant install a 
television antenna or air conditioning units of any type on the roof, in the 
windows or upon the exterior of the Premises. If any such alterations or 
additions are made without such consent, Landlord may correct or remove them, 
and Tenant shall be liable for any and all expenses incurred by Landlord in 
the performance

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of this work. At the termination of this Lease all such alterations or 
improvements made to the Premises shall remain on the Premises and become 
property of the Landlord, unless Landlord directs that such alteration or 
improvements be resolved, in which event Tenant shall restore the Premises 
to their original condition.

14. DAMAGE TO BUILDING OR PREMISES:  If the Premises are damaged or destroyed 
by fire or other casualty from any cause, so as to render the Premises unfit 
for use and occupancy, and such damage and destruction was without the fault 
or neglect of Tenant, his servants, employees, agents, visitors or licensees 
then a prop rata portion of the rent, in accordance with the nature and 
extent of the injury to Premises, shall be suspended or abated until the 
Premises have been repaired. Landlord will proceed at its expense, as 
expeditiously as practicable, to repair the damage, unless, because of the 
extent of the damage or destruction, Landlord should decide not to repair or 
restore the Premises or the Building, in which event and at Landlord's sole 
option, Landlord may terminate this Lease forthwith, by giving Tenant's a 
written notice of its intention to terminate with ninety (90) days after the 
date of the casualty. Notwithstanding the foregoing, in case the fire or 
other casualty shall be caused by the carelessness, negligence or improper 
conduct of Tenant, its agents, servants, employees, visitors or licensees 
then, Tenant shall be liable for the full amount of rental during the period 
of restoration or until cancellation, and all required repairs shall be made 
at Tenants expense. In no event shall Landlord be required to repair, restore 
or rebuild any portions of the premises constituting a part of Tenant's 
leasehold improvements or other Tenant work, trade fixtures, equipment, or 
personal property. No compensation or claim will be paid by Landlord, or 
diminution of rent allowed by Landlord, by reason or inconvenience, annoyance 
or injury to business arising from the necessity of repairing any other 
portion of the Building, however the necessity may occur. Notwithstanding 
any provision contained in this Lease Agreement to the contrary, the Tenant 
shall have the right to terminate this Lease Agreement in the event the 
Premises are damaged to the extent that said premises cannot be restored 
within 210 days next following the date upon which the damage occurs.

15.  HOLD HARMLESS; INSURANCE:  (a) Tenant agrees that it will indemnify and 
save Landlord and its agent(s) harmless of and from any and all liabilities, 
damages, causes of action, suits, claims, judgments, costs and expenses of 
any kind (including attorney's fees) (i) relating to or arising from the 
possession, use, occupation, management, repair, maintenance or control of 
the Premises, or any portion thereof, or (ii) arising from or in connection 
with any act or omission of Tenant or Tenant's agents, employees or invitees, 
or (iii) resulting from any default, violation of nonperformance of this 
Lease by Tenant, or (iv) resulting from injury to person or property or loss 
of life sustained in or about the Premises. To assure such indemnity, Tenant 
shall carry and keep in full force and effect at all times

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during the term of this Lease for the protection of Landlord, its agent(s) 
and Tenant herein, public liability insurance with limits of at least One 
Million Dollars ($1,000,000.00) for each accident and Five Hundred Thousand 
Dollars ($500,000.00) for each separate injury, and property damage insurance 
in the amount of One Hundred Thousand Dollars ($100,000.00). Tenant certifies 
that Landlord and its agent(s) shall be maintained at all times as an 
additional names insured under such insurance policy. In the event Tenant 
shall fail to maintain such policy of insurance then Landlord may, after 
three (3) days' written notice to Tenant, obtain such policy and pay the 
premium thereon and the amount so paid shall be added to the next installment 
of Minimum Rent. (b) It is understood and agreed that all personal property, 
goods, wares and merchandise in the Premises shall be and remain at the sole 
risk of Tenant or those claiming through Tenant, and Landlord shall not be 
liable for any damage to or loss of such personal property, goods, wares and 
merchandise arising from bursting, overflowing or leaking of the roof or of 
water, sewer or steam pipes, or from heating or plumbing fixtures, or from any 
other cause whatsoever, unless said damages are caused through the gross 
negligence of Landlord. Tenant certifies that it has either obtained its own 
insurance coverage for losses to personal property of any kind which may be 
in or on the Premises or has decided to self-insure for such losses.

16.  SUBORDINATION:  Tenant covenants and agrees that all of its rights 
hereunder are and shall be subject and subordinate to the lien of any first 
mortgage hereafter placed on the demised Premises or any part thereof, except 
the Tenant's property or trade fixtures, and to any and all renewals, 
modifications, consolidations, replacements, extensions or substitutions of 
any first mortgage (which is hereinafter termed the mortgage). Such 
subordination shall be automatic, without the execution of any further 
subordination agreement by Tenant. If, however, a written subordination 
agreement, consistent with this provision, is required by a mortgagee, Tenant 
agrees to execute, acknowledge and deliver the same and in the event of 
failure so to do, Landlord may, in addition to other remedies for breach of 
covenant hereunder, execute, acknowledge and deliver the same as the agent or 
attorney in fact of Tenant, and Tenant hereby irrevocably constitutes 
Landlord its attorney-in-fact for such purpose.

17.  ATTORNMENT AND NONDISTURBANCE:  (a) If, at any time during the term of 
this Lease, the Landlord of the demised Premises shall be the holder of a 
leasehold estate covering premises which include the demised Premises, and if 
such leasehold shall terminate or be terminated for any reason, or if, at any 
time during the term of Lease a mortgage to which this Lease is subordinate 
shall be foreclosed, Tenant agrees at the election and upon demand of any 
owner of the premises which include the demised Premises, or of any mortgagee 
in possession thereof, or of any holder of a leasehold thereafter affecting 
premises which include the demised Premises, or of any purchaser

                                       7


at foreclosure, to attorn, from time to time, to any such owner, mortgagee, 
holder or purchaser upon the terms and conditions set forth herein for the 
remainder of the term demised in this Lease. Provided however, that Tenant 
shall not be obligated to attorn unless, if Tenant shall so request in 
writing, such holder, owner, mortgagee or purchaser shall execute and deliver 
to Tenant an instrument wherein said holder, owner, mortgagee or purchaser 
agrees that so long as Tenant performs all the terms, covenants and conditions 
of this Lease, on Tenant's part to be performed, Tenant's possession under the 
provisions of this Lease shall not be disturbed by such holder, owner, 
mortgagee or purchaser.

     (b) The foregoing provisions shall inure to the benefit of any such 
owner, mortgagee, holder or purchaser and shall apply notwithstanding that 
this Lease may terminate upon the termination of any such leasehold estate or 
upon such foreclosure, and shall be self-operative upon any such demand, 
without requiring any further instrument to give effect to such provisions. 
Tenant, however, upon demand of any such owner, mortgagee, holder or 
purchaser, agrees to execute, from time to time, an instrument in 
confirmation of the foregoing provisions, satisfactory to any such owner, 
mortgagee, holder or purchaser, in which Tenant shall acknowledge such 
attornment and set forth herein and shall apply for the remainder of the term 
originally demised in this Lease. Nothing contained in this article shall be 
construed to impair any right otherwise exercisable by any

18. SUBLETTING AND ASSIGNMENT: Tenant will not sublet the Premises or any 
part thereof or transfer possession or occupancy thereof or rent desk space 
therein to any person, firm or corporation or transfer or assign this Lease 
without the prior written consent of Landlord, nor shall any subletting or 
assignment thereof be effected by operation of law or otherwise without the 
prior written consent of Landlord. Further, no such assignment or subletting 
nor the consent of Landlord thereto shall release, discharge or affect the 
liability of Tenant, as provided in this Lease, for the full discharge or 
affect the liability of Tenant, as provided in this Lease, for the full term 
hereof. Any consent by Landlord to an assignment or subletting of this Lease 
shall not constitute a waiver of the necessity for such consent as to any 
subsequent assignment or subletting. If Tenant shall, without the prior 
written consent of Landlord, transfer, assign or hypothecate any stock or 
interest in the Tenant, so as to result in a change in the control thereof by 
the person, persons or entities owning a controlling interest therein as of 
the date of this Lease, then Landlord shall have the option to terminate this 
Lease at any time after actual notice of such change by giving Tenant at 
least sixty (60) days prior written notice and, on the date fixed in such 
notice for termination of this Lease, this Lease shall expire and come to end 
with the same effect as if said date were originally set forth in this Lease 
for expiration of the term. The mere receipt by Landlord or rent from a party 
other than Tenant shall not be deemed actual notice of any change in control 
or ownership of

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Tenant. This provision shall not be applicable to the transfer of any stock 
in the Tenant, to a member of the immediate family or any person(s) owning as 
of the date of this Lease a controlling interest therein (i.e., the spouse and 
direct lineal ancestor or descendant of such person or such person's spouse).

19. CONDEMNATION: This Lease shall terminate and the rental payable hereunder 
shall be abated to the date of such termination in the event of the forceable 
leasing in excess of one year or condemnation of the Premises or any part 
thereof by any competent authority under the right of eminent domain for any 
public or quasi-public use or purposes which renders the balance of the 
Premises economically unsuitable. If the nature, location or extent of any 
proposed condemnation affecting the Building is such that Landlord elects in 
good faith to demolish all or substantially all of the Building, the Landlord 
may terminate this Lease by giving at least sixty (60) days' written notice 
of termination to Tenant at any time after such condemnation, and this Lease 
shall terminate on the date specified in such notice. The forceable leasing 
by any competent authority of any portion of the Building other than the 
Premises shall have no effect whatever upon this Lease. In case of any taking 
or condemnation, whether or not the term of this Lease shall cease and 
terminate, the entire award shall be the property of Landlord, and Tenant 
hereby assigns to Landlord all of his right, title and interest in and to any 
such award. Tenant, however, shall be entitled to claim, prove and receive in 
the condemnation proceeding such awards as may be allowed for fixtures and 
other equipment installed by it, but only if such awards shall be made by the 
Court in addition to the award by it to Landlord for the Land and Building or 
part thereof so taken.

20. QUIET ENJOYMENT: Landlord covenants that, upon performance by Tenant of 
all covenants herein, Tenant shall have and hold the Premises free from 
any interference from Landlord, except as otherwise provided herein.

21. TENANT'S DEFAULT: Tenant shall be in default of this Lease upon 
the happening of any one of the following:

     A. Failure to pay the rent or any other sum required by the terms 
        of this Lease within five (5) days after the due date.

     B. The commencement of any action or proceeding or the dissolution or 
        liquidation of Tenant, or for the appointment of a receiver or trustee 
        of Tenant's property, and the failure to discharge any such action 
        within twenty (20) days.

     C. The making of any assignment for the benefit of creditors, or if 
        Tenant is declared bankrupt.

     D. The abandonment of the Premises by Tenant.

                                       9


     E. Failure to perform or observe any other term, covenant or condition 
        of this Lease and the continuance therefore for twenty (20) days 
        after written notice from Landlord. In addition to any other remedies 
        contained herein the Landlord at his sole discretion may convert this 
        Lease to a month-to-month lease if the Tenant has been in default for 
        any rent or other amounts owned for over (30) days.

     Upon default, as hereinabove defined, Landlord, without notice to 
Tenant, may enter upon the Premises without terminating this Lease and do any 
acts which Landlord may deem necessary to cure such default, and Tenant 
agrees to pay Landlord any damage and/or expense incurred thereby. 
Furthermore, upon default Landlord may, on ten (10) days advance written notice 
to Tenant, terminate this Lease and, with or without legal process, take 
possession of the Premises and remove Tenant or any other occupant. Landlord 
shall be entitled to recover as damages from Tenant an amount equal to the 
balance of all rent due to the end of the Lease term, together with all legal 
and other expenses incurred, including the cost of reletting the Premises. 
Tenant shall be credited however, with any net amounts received by Landlord 
from the reletting of the Premises. No act of Landlord shall be considered 
an acceptance of a surrender of the Premises, unless in writing. Landlord may 
maintain separate actions each month to recover the damages, without waiting 
to the end of the term of this Lease.

22. LEGAL EXPENSES: If any action or proceeding is commenced in which Landlord 
intervenes or is made a party by reason of being the Landlord under the 
Lease, or if Landlord shall deem it necessary to engage attorneys or institute 
any suit against Tenant in connection with the enforcement of Landlord's 
rights under the Lease, the violation of any term of the Lease, the 
declaration of Landlord's rights hereunder, or the protection of Landlord's 
interests under the Lease, Tenant shall reimburse Landlord for its expenses 
incurred as a result thereof including, without limitation, court costs and 
reasonable attorneys' fees.

23. SURRENDER OF PREMISES: Upon the expiration or termination of this Lease, 
Tenant shall quit and surrender the Premises to Landlord broom clean and in 
good order ordinary wear and tear excepted, and shall remove all of its 
property therefrom provided, however, that upon surrender of the premises, it 
is in compliance with all applicable building code requirements. The 
obligations of this Paragraph shall survive the termination of this Lease. In 
the event Tenant fails to remove furniture, trade fixtures or machinery 
from the Premises before the expiration of this Lease, it is agreed that Tenant 
is abandoning said furniture, trade fixtures and machinery and the same shall 
become the property of Landlord, who shall have the right to use, remove or 
dispose of same at Tenant's expense.

                                      10


24, TENANT HOLDING OVER: If Tenant shall not immediately surrender possession 
of the Premises at the termination of the Lease, Tenant shall become a tenant
month-to-month, provided rent shall be paid to and accepted by Landlord in 
advance at twice the Minimum Rent payable hereunder just prior to the 
termination of this Lease; but unless and until Landlord shall accept such 
rental from Tenant, Landlord shall continue to be entitled to retake or 
recover possession of the Premises as hereinbefore provided in case of default 
on the part of Tenant, and Tenant shall be liable to Landlord for any loss or 
damage Landlord may sustain by reason of Tenant's failure to surrender 
possession of the Premises immediately upon the expiration of the term of this 
Lease. If Tenant shall fail to surrender possession of the Premises 
immediately upon the expiration of the term hereof, Tenant hereby agrees that 
all obligations of Tenant and all rights of Landlord application during the 
term of this Lease shall be equally applicable during such period of 
subsequent occupancy, whether or not a month-to-month tenancy shall have been 
created as aforesaid.

25. LANDLORD'S LIABILITY: In no event shall Landlord including any successor 
assignee of all or any portion of Landlord's interest in the Building or Land, 
be personally liable or accountable with respect to any provision of this 
Lease. If Landlord shall be in breach or default with respect to 
any obligation hereunder or otherwise, Tenant agrees to look for satisfaction 
solely to the equity of Landlord in the Building and Land. The liability of 
Landlord, or other entity comprising Landlord, shall in no event exceed the 
amount of such equity and no other assets of Landlord (or any partners, 
stockholders or officers of Landlord) shall be subject to levy, execution or 
other procedures for satisfaction of Tenant's remedies. In the event Landlord 
transfers this Lease, other than as security for a mortgage, ground lease or 
deed of trust, Landlord (and, in case of any subsequent transfers or 
conveyance, than grantor) shall, upon such transfer and acceptance by the 
transferee be relieved from all liability and obligation hereunder arising 
after such transfer, including any liability to Tenant for any security 
deposit under this Lease.

26. NOTICES: All notices, demands, request, approvals, consents or other 
instrument required or desired to be given hereunder by either party to the 
other shall be personally delivered or sent by U.S. certified or registered 
mail, return receipt requested, first class postage prepaid, addressed as 
follows: If to Landlord: Botzler Emery Associates Guilford Ten Limited 
Partnership, c/o Pledge, 9570 Berger Road, Columbia, MD 21046 Attn: Larry 
Ohler, with a copy to Aid Association for Lutherans, 4321 N. Ballard Road, 
Appleton, WI 54919. If to Tenant: PATS, Inc., 9570 Berger Road, Columbia, MD 
21046.

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27. ESTOPPEL CERTIFICATES: Tenant agrees from time to time, within five (5) 
business days of request from Landlord, to execute, acknowledge and deliver 
to Landlord or to such other person(s) as Landlord may indicate a statement 
in writing certifying that Tenant is in possession of the Premises and 
currently paying rent at the then-applicable Minimum Rent and that this Lease 
is in full force and effect, and containing such other information as may be 
required.

28. SUCCESSOR AND ASSIGNS: This Lease and the covenants and conditions herein 
contained shall inure to the benefit of and be binding upon Landlord, its 
successors and assigns, and shall inure to the benefit of and be binding upon 
Tenant, its heirs, distributees, personal representatives, successors and 
assigns, provided that as to the assign of Tenant, the benefits shall inure 
to such assigns only if the assignment has been consented to in writing by 
Landlord.

29. ENTIRE AGREEMENT: This Lease contains the entire agreement of the parties 
in regard to the Premises. There are no oral agreements existing between them.

30. WAIVER OF JURY TRIAL: Tenant hereby waives all right to trial by jury 
in any claim, action, proceeding or counterclaim by either Landlord or Tenant 
against the other or any matters arising out of or in any way connected with 
this Lease, the relationship of Landlord and Tenant and/or Tenant's use of 
occupancy of the Premises.

31. OTHER PROVISIONS: This Lease shall be construed and governed by the law of 
the State of Maryland. No waiver of any breach of any covenant, condition or 
agreement contained herein shall operate as a waiver of the covenant, 
condition or agreement itself, or of any subsequent breach thereof. If any 
term, covenant or condition of this Lease or the application thereof to any 
person or circumstance shall to any extent be invalid or unenforceable, the 
remainder of this Lease or the application of such term, covenant or condition 
to persons or circumstances other than those as to which it is held invalid 
or unenforceable, shall not be affected thereby and each term, covenant and 
condition of this Lease shall be valid and enforced to the fullest extent 
permitted by law. Except as specifically provided for herein, Tenant agrees 
to accept the Premises in its "as is" condition.

32. JURISDICTION: Tenant hereby consents to the exercise of personal 
jurisdiction over it by any federal or state court in the State of Maryland 
and consents to the laying of venue in any jurisdiction or locality within 
the State of Maryland. In addition to (and not in lieu of) the agents 
designated under applicable law for purposes of service of process, Tenant 
appoints Larry D. Ohler having an address at 9570 Berger Road, Columbia, MD 
21046 as Tenant's agent for receipt of service of process on Tenant's behalf 
in connection with any suit, writ, attachment, execution or discovery or 
supplementary proceedings

                                      12


in connection with the enforcement of this Lease. Service on said agent shall 
be effected by any means permitted under applicable law or by the court in 
which the action is filed, or, at Landlord's option, by mailing process, 
postage prepaid, by certified mail, return receipt requested, either to 
Tenant's agent at the foregoing address or to Tenant at the address set forth 
in Section 2c of this Lease. Service shall be deemed effective upon receipt. 
The Tenant may designate a change of address by written notice to the other 
given by certified mail, return receipt requested, at least ten (10) days 
before such change of address is to become effective.

33. LANDLORD'S RIGHT TO CURE:  If Tenant shall fail to perform any covenant 
or duty required of it by this Lease or by law, Landlord shall, after notice 
to Tenant and expiration of the applicable cure period, have the right (but 
not the duty) to enter the Premises, if necessary, to perform the same 
without notice, but the reasonable cost thereof shall be deemed to be 
additional rent, and shall give the Landlord the same rights and remedies as 
though the additional rent were part of the monthly rent due the Landlord 
under this Lease.

IN WITNESS WHEREOF, Landlord and Tenant have executed this Lease under seal 
as of the day and year first above written.

WITNESS                                PLEDGC
                                       PARTNERSHIP

/s/ Edward Tindall                     /s/ Charles L. Parrington
- -----------------------------------    -----------------------------------    
Edward Tindall                         Charles L. Parrington
                                       General Partner
                                       ("Landlord")

                                       PATS, INC.

/s/ L. Roland Sturm                    By: /s/ Harvey O. Patrick
- -----------------------------------       --------------------------------    
L. Roland Sturm                           Harvey O. Patrick
                                       ("Tenant")


                                     13


                              AMENDMENT OF LEASE


     THIS AMENDMENT is made as of this 1st day of July, 1997, by and between 
PLEDGC, a Maryland general partnership, as General Partner of Botzler-Emory 
Associates Guilford Ten Limited Partnership, a Maryland limited partnership 
(hereinafter referred to as "Landlord"), and PATS, INC., a Maryland 
corporation (hereinafter referred to as "Tenant").

     WHEREAS, Landlord and Tenant entered into a lease dated June 1, 1992, 
regarding the premises described as 9570 Berger Road, Columbia, Howard 
County, Maryland containing 65,923 square feet of space, more or less (the 
"Property"); and

     WHEREAS, the parties hereto desire to amend the Lease as hereinafter set 
forth. 

     NOW, THEREFORE, WITNESSETH for good and valuable consideration, the 
mutual receipt and sufficiency of which are hereby acknowledged, the parties 
agree as follows:

     1.   Paragraph 4 of the Lease is amended as follows:

          RENT. Tenant shall pay to Landlord minimum rent ("Rent") at the 
     rate of Four Hundred Five Thousand Dollars ($405,000.00) per annum, 
     payable in equal monthly installments of Thirty-Three Thousand Seven 
     Hundred Fifty Dollars ($33,750.00) in advance and without demand 
     beginning on the first day of July 1997 and continuing on the first day 
     of each month thereafter subject to the adjustments set forth herein.

     2.   Paragraph 5 of the Lease is amended as follows:

          RENT ADJUSTMENT. The Rent shall be adjusted annually beginning on 
     July 1, 1998 and on the first day of July of each succeeding year during 
     the term of the Lease to a sum obtained by multiplying the rent for the 
     year beginning July 1, 1997 by a fraction, the numerator of which shall 
     be the amount of the CONSUMER'S PRICE INDEX for Baltimore, Maryland (the 
     "Index") for the preceding December (or the most recently available 
     monthly Index on July 1 of each

                                      1



     year) and the denominator of which shall be such Index for July 1, 1997; 
     provided, however, that in no event shall the annual rent increase be 
     less than three percent (3%) annually each July 1, beginning July 1, 
     1998 during the term hereof. As used herein, the term "Consumer's Price 
     Index" means the Consumer's Price Index for "all items" now published by 
     the Bureau of Labor statistics of the United States Department of Labor, 
     or if such publication is discontinued, then the most closely comparable 
     data published by such agency or another agency of the United States 
     Government.

     3.   Paragraph 2 of the Lease is amended to extend the Lease term as 
follows:

          The term of the Lease shall end on June 30, 2007.

     4.   The following provision is added to the Lease:

          RIGHT OF FIRST REFUSAL. If, at any time after the date of this 
     Amendment, the Landlord shall desire to sell the property or any part 
     thereof, or shall receive from a third party a bona fide offer to 
     purchase the property, or any part thereof, the Landlord, before making 
     or accepting the offer, as the case may be, shall send to the Tenant 
     written notification from the Landlord of the Landlord's intention to 
     make or accept the offer unless the Tenant agrees to purchase the 
     property for the greater of Three Million Three Hundred Thousand Dollars 
     ($3,300,000.00) or the fair market value of the property. The Tenant 
     shall have twenty (20) days from the date of the Notice to notify 
     Landlord in writing of Tenant's election to exercise its right to 
     purchase the property.

          If the Tenant exercises its right to purchase the property, the 
     parties shall select by mutual agreement an appraiser to establish the 
     fair market value of the property. If the parties are unable to agree on 
     the appraiser to be used, each party shall select their own appraiser 
     (and be responsible for their respective costs thereof) and the average 
     of the two appraisers shall be deemed the fair market value for 
     establishing the purchase price by the Tenant. Tenant shall have ten 
     (10) days from final determination of the fair market value to advise 
     Landlord in writing whether Tenant intends to proceed to exercise 
     Tenant's right of that refusal. Settlement of the purchase by the Tenant 
     shall occur within sixty (60) days after the date of the Tenant's notice 
     following the final determination of fair market value.

                                      2



          If the Tenant does not elect to exercise its right of first refusal 
     in the manner set forth above, then the Landlord shall be free for a 
     period of ninety (90) days from the expiration of the ten (10) day 
     notice period after the determination of fair market value to sell the 
     property free and clear of the right of first refusal. In the event that 
     the property is not sold to a third party within the ninety (90) day 
     period, then any further sale of the property must first be submitted to 
     the Tenant in accordance with the provisions of this paragraph.

          The Tenant's right of first refusal shall be subordinate and junior 
     to the legal operation and effect of any present or future mortgage or 
     Deed of Trust which now or hereafter becomes a lien on the property.

          Anything in this Agreement to the contrary notwithstanding, this 
     right of first refusal and the rights and obligations contained herein 
     shall automatically expire if not exercised on or before June 30, 2007.

     5.   In all other respects, the Lease shall remain in full force and 
effect.

     6.   This Amendment shall be binding upon the parties hereto and their 
respective successors and assigns.

     7.   This Amendment shall be interpreted and construed in accordance 
with the laws of the State of Maryland.

     WITNESS the hands and seals of the parties hereto as of the day and year 
first above written.

ATTEST/WITNESS:                        LANDLORD: BOTZLER-EMORY
                                       ASSOCIATES GUILFORD TEN
                                       LIMITED PARTNERSHIP

                                   By: PLEDGC, a Maryland General
                                       Partnership, General Partner

/s/ Harry S. Jackson                   By: Edward G. Tindall             (SEAL)
- --------------------------------          -------------------------------
Harry S. Jackson                           Edward G. Tindall             

                                      3



ATTEST/WITNESS:                        TENANT:

                                       PATS, INC.

/s/ Joan Lewis                         By: /s/ Harvey O. Patrick         (SEAL)
- --------------------------------          -------------------------------



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