THIS FIFTEENTH AMENDMENT TO CREDIT AGREEMENT (this "Amendment") is made
and  entered  into as of the  13th  day of  October  1995,  by and  among  Telos
Corporation,  a Maryland  corporation  (formerly  known as C3,  Inc., a Maryland
corporation),   Telos  Corporation,   a  California  corporation   (individually
"Borrower" and collectively  "Borrowers") and  NationsBank,  N.A.,  successor by
merger to American Security Bank, N.A. (the "Bank" or "Agent").

                                   WITNESSETH:

         A.  Borrowers,  the  Bank  and the  Agent  entered  into  that  certain
Revolving and Reducing Senior Facility Credit Agreement, dated as of January 14,
1992 (the "Original Credit Agreement").

         B.  Borrowers,  the Bank and the Agent  entered into an  Agreement  and
Waiver dated as of July 20, 1992,  an Amendment  dated as of October 1, 1992, an
Amendment  dated as of January 15, 1993, an Amendment dated as of June 30, 1993,
an Amendment  dated as of August 31, 1993,  an Amendment  dated as of October 5,
1993, an Amendment dated as of December 31, 1993, an Amendment dated as of April
11,  1994,  an  Amendment  dated as of June 8, 1994,  an  Amendment  dated as of
October 7, 1994, an Amendment dated as of January 5, 1995, an Amendment dated as
of January 12, 1995, an Amendment and Waiver dated as of April 17, 1995,  and an
Amendment dated as of August 4, 1995, whereby Borrowers,  the Agent and the Bank
agreed,  among other things, to amend certain  provisions of the Original Credit
Agreement (the Original Credit  Agreement,  as so amended,  shall be hereinafter
referred to as the "Credit Agreement").

         C.  Borrowers,  the Agent and the Bank now desire,  pursuant to Section
11.1 of the Credit  Agreement,  to amend certain other  provisions of the Credit
Agreement on the terms and conditions set forth below.

         NOW  THEREFORE,  for good and valuable  consideration,  the receipt and
sufficiency  of which are hereby  acknowledged,  the  parties,  intending  to be
legally bound, hereby agree as follows:

         Section  1.  Definitions.  All  terms  used in this  Amendment  and not
otherwise  defined shall have the meanings  ascribed to such terms in the Credit
Agreement.

         Section 2. Amendment to Definitions.
                    -------------------------
         (a)  Pursuant to Section 11.1 of the Credit  Agreement,  Section 1.2 of
the  Credit  Agreement  is  hereby  amended  by the  addition  of the  following
definitions in the appropriate place therein:

         "Investor   Notes:   collectively,   those  certain   Series  B  Senior



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Subordinated Secured Notes Due October 1, 2000 and those certain Series C Senior
Subordinated  Unsecured  Notes Due October 1, 2000,  each dated October 13, 1995
and  subordinated  in right of payment in the manner and to the extent set forth
in the Investor Subordination Agreement."

         "Investor Subordination Agreement: that certain Subordination Agreement
dated as of October 13, 1995 among the Bank,  Borrowers  and each of the holders
of the Investor Notes."

         (b) The definition of  "Subordinated  Debt" in the Credit  Agreement is
hereby  amended  to  include  the  Investor  Notes  and any and all  extensions,
renewals, replacements,  refinancings and refundings of the same. All references
to  "Subordinated  Debt" in the Credit  Agreement shall be deemed to include the
debt  evidenced  by the  Investor  Notes  and  any  such  extensions,  renewals,
replacements, refinancings and refundings of the same.

         Section 3. Amendments Regarding Overadvance Amount.
                    ---------------------------------------
         (a)  Pursuant  to  Section  11.1  of  the  Credit  Agreement,   Section
2.1(a)(ii) is hereby deleted and amended in its entirety to read as follows:

         "The Commitment shall include an overadvance amount of $4,000,000 which
amount shall be  automatically  reduced to  $2,000,000  on February 1, 1996 (the
"Overadvance  Amount").  The  Overadvance  Amount  is an  incremental  borrowing
availability  under the  Commitment  in  addition  to the  Borrowing  Base.  The
availability of Loans under the Overadvance Amount is subject to and conditioned
upon the  commencement  of that  certain  Army  contract  #DAHC94-95-D-0010  and
continued delivery order activity  thereunder,  as determined by the Bank in its
sole  discretion,  based upon  Borrowers'  quarterly  backlog  reports and other
information available to the Bank."

         (b)  Pursuant  to  Section  11.1 of the  Credit  Agreement,  the second
sentence of Section 2.1(d) of the Credit Agreement is hereby deleted and amended
in its entirety to read as follows:

         "Loans evidencing any or all of the Overadvance  Amount shall mature on
June  30,  1996 or on such  earlier  date on  which  the  Loans  evidencing  the
Overadvance Amount become due and payable as otherwise herein provided,  whether
by declaration of  acceleration,  optional or mandatory  prepayment or otherwise
(the "Overadvance Maturity Date")."

         Section 4. Additional Fees.
                    ---------------
         Pursuant to Section  11.1 of the Credit  Agreement,  Section 2.6 of the
Credit Agreement is hereby amended by the addition of the following  subsections
(k) and (l):

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         "(k)  Overadvance  Extension  Fee.  On  or  before  October  13,  1995,
Borrowers shall pay to the Agent an overadvance extension fee equal to $25,000.

         (l)  Underwriting  Fee. On or before October 13, 1995,  Borrowers shall
pay to the Agent an underwriting fee equal to $10,000.

         Section 5. Amendment to Mandatory Prepayments.
                    ----------------------------------
         Pursuant to Section  11.1 of the Credit  Agreement,  Section 2.8 of the
Credit  Agreement is hereby amended by the addition of the following  subsection
(f):

         "(f) At the option of the Agent, there shall be a mandatory  prepayment
of the Loans in full in the event that any prepayment, or any event which causes
a prepayment,  of all or any portion of the outstanding  principal amount of the
Investor Notes occurs,  including,  but not limited to: (i) the distribution and
sale of common stock of either  Borrower  pursuant to an effective  registration
statement (some of the proceeds of which sale are available to such Borrower) in
one or more public offerings (other than a registration statement on Form S-4 or
Form S-8)  which has been filed with the  Commission  and has become  effective;
(ii) any sale of  securities  of  either  Borrower,  which  results  in net cash
proceeds to such Borrower in excess of  $1,000,000,  other than (A)  obligations
for  borrowed  money due  within  one year and (B) other  obligations  for money
borrowed from the Bank and/or its successors,  substitutes and  participants and
their respective assigns and any refinancing  thereof;  or (iii) any Merger. For
purposes of this Section 2.8(f),  "Merger" shall mean a merger  consolidation or
other combination to which either Borrower is a party, in which such Borrower is
not a surviving  corporation or which results in the  acquisition of "beneficial
ownership" of securities of such Borrower  representing 50% or more of the total
number of votes that may be cast for the  election of  directors by any "person"
or "group"  (as such  terms are  defined  in Rule  13(d)  promulgated  under the
Exchange  Act),  or a sale by such Borrower of all or  substantially  all of its
assets."

         Section 6. Amendment to Negative Covenants.
                    -------------------------------
         (a)  Pursuant to Section 11.1 of the Credit  Agreement,  Section 6.2 of
the  Credit  Agreement  is  hereby  amended  by the  addition  of the  following
subsection

(j):

         "(j) the PP&E Lien referred to in the Investor Subordination Agreement,
subject,  however,  to the prior approval by the Bank of any security agreement,
collateral assignment,  mortgage or other agreement or instrument giving rise to
such  Lien  and  all  related  documents  and  instruments,  including,  without
limitation, financing statements.


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         (b) Pursuant to Section 11.1 of the Credit Agreement, Article VI of the
Credit Agreement is amended by the addition of the following Section 6.19:

         "6.19    Prior Approval of Security Agreements.
                  -------------------------------------
         Neither  Borrower  nor any  Subsidiary  shall  enter into any  security
agreement  collateral  assignment,  mortgage or other  agreement,  instrument or
document (including, without limitation,  financing statements) which gives rise
to, creates or perfects a Lien against either  Borrower or a Subsidiary,  unless
the Bank  approves,  in its sole  discretion,  the  form and  substance  of such
agreement, instrument or other document."

         Section 7. Amendment to Financial Covenants.
                    ---------------------------------
         (a)  Pursuant to Section 11.1 of the Credit  Agreement,  Section 7.2 of
the Credit  Agreement  is hereby  deleted and amended in its entirety to read as
follows:

         "7.2 Minimum Tangible Capital Funds. On a consolidated basis,  Tangible
Capital Funds shall not be less than the following during the periods  described
below:

                  Period                                 Required Amount
                  ------                                 ---------------
         October 13, 1995 through                          ($9,250,000)
                  December 30, 1995
         December 30, 1995 through                         ($8,500,000)
                  the Maturity Date"

         (b)  Pursuant to Section 11.1 of the Credit  Agreement,  Section 7.4 is
hereby deleted and amended in its entirety to read as follows:

         "7.4.  Leverage  Ratio.  On a  consolidated  basis,  the ratio of Total
Liabilities minus Subordinated Debt to Net Worth plus Subordinated Debt will not
at any time exceed 5.0 :1."

         Section 8. Confidentiality Provisions.
                    --------------------------
         In  connection  with this  Amendment  and the execution and delivery by
Telos  Corporation  (formerly  C3) of the Investor  Notes,  the Bank may request
access to confidential  opinions,  analyses and advice furnished to Borrowers or
their Board of Directors by outside accountants and other financial advisors. In
the event that the Bank receives access to such information,  the Bank agrees to
keep such  information  in  confidence  and shall not disclose,  communicate  or
divulge such  information to any other party, and shall not use such information
for any other purpose,  except 

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that  the  Bank  may  share  such  information,   to  the  extent  necessary  or
appropriate, with its outside legal counsel, auditors and regulators.

         Section 9. Conditions Precedent to the Effectiveness of this Amendment.
                    ------------------------------------------------------------
         The  provisions of this Amendment are  conditioned  upon, and shall not
become effective until the occurrence of, each of the following:

                           (a)  Borrowers  shall  have  delivered  to the  Agent
                           certified   corporate   resolutions   approving   the
                           transactions described herein, the form and substance
                           of which  shall be  satisfactory  to the Agent in its
                           sole and absolute discretion.

                           (b) The Agent  shall  have  received  the  opinion of
                           Borrowers'    counsel    regarding    the    Investor
                           Subordination  Agreement,  the form and  substance of
                           which shall be  satisfactory to the Agent in its sole
                           and absolute discretion.

                           (c)  The  Agent  shall  have  received   evidence  of
                           authority and  incumbency  for each of the holders of
                           the Investor  Notes,  the form and substance of which
                           shall be  satisfactory  to the  Agent in its sole and
                           absolute discretion.

                           (d) The Agent  shall  have  received  from  Borrowers
                           and/or their outside auditors assurances satisfactory
                           to  Agent,  in  its  sole  and  absolute  discretion,
                           regarding the accounting  treatment applicable to the
                           Investor Notes and the payment obligations  evidenced
                           thereby.

                           (e)  Borrowers  shall have paid to the Agent all fees
                           due and payable on and as of the date hereof.

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                           (f) No  litigation,  proceeding  or any other  action
                           shall have been filed,  or threatened to be filed, by
                           any party which challenges, seeks to enjoin, restrain
                           or  prohibit  or to obtain  damages  in respect of or
                           which is related to the transactions  contemplated by
                           this Amendment.




         Section 10. No Waiver.
                     ---------
         Notwithstanding  execution of this Amendment and the extension of Loans
by the Bank to Borrowers in accordance with the provisions  hereof,  neither the
Bank nor the Agent is waiving,  and shall not be deemed to have  waived,  any of
their respective rights under any provisions of the Credit  Agreement,  the Note
or the other  Revolving  Loan  Documents.  The Bank's or the Agent's  failure to
insist upon the strict performance of any term, condition, or other provision of
the Credit  Agreement,  the Note or the other  Revolving  Loan  Documents  or to
exercise any right or remedy  hereunder  or  thereunder  shall not  constitute a
waiver by the Bank or the Agent of any such term,  condition or other  provision
or default or Event of Default in connection therewith.

         Section 11. Continued Effect of Credit Agreement.
                     ------------------------------------
         Except as  specifically  amended  herein,  the Credit  Agreement is and
shall  continue  to be in full  force  and  effect  and is hereby  ratified  and
confirmed in all respects.

         Section 12. Counterparts.
                     ------------
         This  Amendment  may be  executed in one or more  counterparts,  all of
which shall be considered one and the same Amendment, and shall become effective
when  one or more of the  same  counterparts  have  been  signed  by each of the
parties to this Amendment and delivered (by facsimile or otherwise) to the other
parties, it being understood that each party need not sign the same counterpart.



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         IN WITNESS  WHEREOF,  the Bank,  the  Agent,  and  Borrowers  have each
executed this Amendment as of the date first written above.

                                    NATIONSBANK, N.A.

                                    By:  /s/  Catherine S. Grimm
                                       ----------------------------
                                    Name:  Catherine S. Grimm
                                          -------------------------
                                    Title:            VP
                                          -------------------------

                                    NATIONSBANK, N.A., as the Agent

                                    By:  /s/  Catherine S. Grimm
                                       ----------------------------
                                    Name:  Catherine S. Grimm
                                          -------------------------
                                    Title:            VP
                                          -------------------------

                                    TELOS CORPORATION, formerly known as
                                    C3, Inc.

                                    By:  /s/  William L.P. Brownley
                                       ----------------------------
                                    Name:   William L.P. Brownley
                                          -------------------------
                                    Title:Vice President and General Counsel
                                          ----------------------------------

                                    TELOS CORPORATION

                                    By:  /s/  William L.P. Brownley
                                       ----------------------------
                                    Name:   William L.P. Brownley
                                          -------------------------
                                    Title:Vice President and General Counsel
                                          -----------------------------------


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