COMMITTED LINE OF CREDIT NOTE
                               (Index LIBOR Note)


$12,000,000.00                                                  February 3, 2000


FOR  VALUE  RECEIVED,  STV  GROUP,  INCORPORATED  and STV  INCORPORATED  and its
SUBSIDIARIES  listed on the attached  Schedule A (individually and collectively,
the  "Borrower"),  with an  address  at 205  West  Welsh  Drive,  Douglassville,
Pennsylvania  19518,  promises  to pay  to  the  order  of  PNC  BANK,  NATIONAL
ASSOCIATION  (the  "Bank"),  in lawful money of the United  States of America in
immediately  available  funds at its  offices  located  at 1600  Market  Street,
Philadelphia,  Pennsylvania,  19103,  or at such other  location as the Bank may
designate  from  time to time,  the  principal  sum of  TWELVE  MILLION  DOLLARS
($12,000,000.00) (the "Facility") or such lesser amount as may be advanced to or
for the benefit of the Borrower  hereunder,  together with interest  accruing on
the outstanding principal balance from the date hereof, as provided below:

1. Rate of Interest.  The principal amount outstanding under this Note will bear
interest  at a rate per annum  (computed  on the basis of  actual  days  elapsed
within a year consisting of 360 days) equal to the sum of (A) LIBOR plus (B) two
hundred (200) basis points (2.0%) (the "Applicable LIBOR"). The Applicable LIBOR
shall remain in effect until  adjusted by the Bank as of the first  calendar day
of each month, without notice to the Borrower.

For the purpose hereof, the following terms shall have the following meanings:

                           "Business Day" shall mean any day on which commercial
         banks settle payments in U.S. dollars in New York City and London other
         than a Saturday or Sunday or a legal holiday on which  commercial banks
         are  authorized or required to be closed for business in  Philadelphia,
         Pennsylvania.

                           "LIBOR" shall mean,  for all advances  outstanding at
         any time during any month,  the interest  rate per annum  determined by
         the Bank by  dividing  (the  resulting  quotient  rounded  upwards,  if
         necessary,  to the nearest  1/100th of 1%) (i) the  Published  Rate for
         such  month by (ii) a number  equal to 1.00  minus  the  LIBOR  Reserve
         Percentage.  As used  herein,  "Published  Rate" shall mean the rate of
         interest  published on the first Business Day of each month in The Wall
         Street  Journal  "Money  Rates"  listing  under  the  caption   "London
         Interbank Offered Rates" for a one month period (or, if no such rate is
         published  therein for any reason,  then such rate published therein on
         the most  recent  Business  Day prior to the  first day of such  month;
         provided,  that if no such rate of  interest is  published  therein for
         longer than 30 consecutive  days,  then the Published Rate shall be the
         eurodollar  rate  for a one  month  period,  as  published  in  another
         publication determined by the Bank).

                           "LIBOR  Reserve  Percentage"  shall mean the  maximum
         effective  percentage  in effect on such day as prescribed by the Board
         of  Governors  of the Federal  Reserve  System (or any  successor)  for
         determining the reserve requirements (including, without limitation,

<PAGE>


         supplemental, marginal and emergency reserve requirements) with respect
         to  eurocurrency   funding  (currently  referred  to  as  "Eurocurrency
         liabilities").

LIBOR shall be adjusted on the effective date of any change in the LIBOR Reserve
Percentage as of such  effective  date. The Bank shall give prompt notice to the
Borrower  of LIBOR as  determined  or  adjusted in  accordance  herewith,  which
determination shall be conclusive absent manifest error.

If the Bank determines (which determination shall be final and conclusive) that,
by reason of circumstances  affecting the eurodollar market generally,  deposits
in dollars (in the  applicable  amounts)  are not being  offered to banks in the
eurodollar  market for the  selected  term,  or adequate  means do not exist for
ascertaining  LIBOR,  then the Bank shall give notice  thereof to the  Borrower.
Thereafter,  until the Bank notifies the Borrower that the circumstances  giving
rise to such suspension no longer exist,  (a) the availability of the Applicable
LIBOR  shall be  suspended,  and (b) the  interest  rate for all  advances  then
bearing  interest under the Applicable LIBOR shall be converted on the first day
of the next calendar  month to a rate of interest per annum  (calculated  on the
basis of actual days elapsed within a year  consisting of 360 days) equal to the
Prime Rate (the  "Applicable Base Rate").  For purposes hereof,  the term "Prime
Rate" shall mean the rate  publicly  announced  by the Bank from time to time as
its prime rate. The Prime Rate is determined  from time to time by the Bank as a
means of pricing some loans to its borrowers.  The Prime Rate is not tied to any
external rate of interest or index, and does not necessarily  reflect the lowest
rate of  interest  actually  charged  by the  Bank to any  particular  class  or
category of customers.  If and when the Prime Rate changes, the rate of interest
with respect to any amounts  hereunder to which the Applicable Base Rate applies
will change automatically without notice to the Borrower,  effective on the date
of any such change.

In addition,  if, after the date of this Note, the Bank shall  determine  (which
determination shall be final and conclusive) that any enactment, promulgation or
adoption of or any change in any  applicable  law,  rule or  regulation,  or any
change  in  the  interpretation  or  administration  thereof  by a  governmental
authority,  central bank or comparable agency charged with the interpretation or
administration thereof, or compliance by the Bank with any guideline, request or
directive  (whether  or not  having  the  force of law) of any  such  authority,
central bank or comparable  agency shall make it unlawful or impossible  for the
Bank to make or maintain or fund loans bearing  interest based on the Applicable
LIBOR,  the Bank shall notify the Borrower.  Upon receipt of such notice,  until
the Bank  notifies  the  Borrower  that the  circumstances  giving  rise to such
determination  no longer apply,  (a) the  availability  of the Applicable  LIBOR
shall be  suspended,  and (b) the  interest  rate on all  advances  then bearing
interest  under the Applicable  LIBOR shall be converted to the Applicable  Base
Rate  either (i) on the first day of the next  calendar  month,  if the Bank may
lawfully  continue to maintain  advances at the Applicable LIBOR to such day, or
(ii)  immediately  if the Bank may not  lawfully  continue to maintain  advances
under the Applicable LIBOR.

In no event will the rate of interest  hereunder exceed the maximum rate allowed
by law.

2. Advances.  The Borrower may borrow,  repay and reborrow  hereunder  until the
Expiration  Date,  subject to the terms and conditions of this Note and the Loan
Documents (as defined  herein).  The "Expiration  Date" shall mean December ___,
2001, or such later date as may be designated by the Bank by written notice from
the Bank to the Borrower.  The Borrower acknowledges and agrees that in no event
will the Bank be under any  obligation  to extend or renew the  Facility or this
Note  beyond  the  Expiration  Date.  In no event  shall  the  aggregate  unpaid
principal  amount of  advances  under this Note  exceed the face  amount of this
Note.


                                      -2-
<PAGE>


3. Advance Procedures.  A request for advance made by telephone must be promptly
confirmed  in  writing  by such  method as the Bank may  require.  The  Borrower
authorizes  the Bank to accept  telephonic  requests for advances,  and the Bank
shall be  entitled  to rely upon the  authority  of any  person  providing  such
instructions.  The Borrower hereby  indemnifies and holds the Bank harmless from
and  against  any and all  damages,  losses,  liabilities,  costs  and  expenses
(including  reasonable  attorneys'  fees and  expenses)  which  may  arise or be
created by the  acceptance of such  telephone  requests or making such advances.
The Bank will  enter on its books and  records,  which  entry  when made will be
presumed correct,  the date and amount of each advance,  as well as the date and
amount of each payment made by the Borrower.

4. Payment Terms. Accrued interest will be due and payable monthly in arrears on
the first day of each month,  beginning  with the  payment due on  _____________
___, 2000. The outstanding principal balance and any accrued but unpaid interest
shall be due and payable on the Expiration Date.

If any payment under this Note shall become due on a Saturday,  Sunday or public
holiday under the laws of the State where the Bank's office  indicated  above is
located, such payment shall be made on the next succeeding business day and such
extension of time shall be included in  computing  interest in  connection  with
such payment.  The Borrower hereby  authorizes the Bank to charge the Borrower's
deposit  account  at the  Bank for any  payment  when  due  hereunder.  Payments
received  will be applied to charges,  fees and expenses  (including  attorneys'
fees),  accrued interest and principal in any order the Bank may choose,  in its
sole discretion.

5. Late  Payments;  Default Rate.  If the Borrower  fails to make any payment of
principal,  interest or other amount  coming due pursuant to the  provisions  of
this Note within 15 calendar days of the date due and payable, the Borrower also
shall pay to the Bank a late charge  equal to the lesser of five percent (5%) of
the amount of such  payment or $100.00 (the "Late  Charge").  Such 15 day period
shall not be  construed  in any way to extend the due date of any such  payment.
Upon maturity,  whether by acceleration,  demand or otherwise, and at the Bank's
option upon the occurrence of any Event of Default (as hereinafter  defined) and
during the  continuance  thereof,  this Note shall bear  interest  at a rate per
annum (based on a year of 360 days and actual days  elapsed)  which shall be two
percentage  points  (2%) in excess of the  interest  rate in effect from time to
time  under  this Note but not more than the  maximum  rate  allowed by law (the
"Default  Rate").  The  Default  Rate  shall  continue  to apply  whether or not
judgment  shall be entered on this Note.  Both the Late  Charge and the  Default
Rate are imposed as  liquidated  damages for the purpose of defraying the Bank's
expenses  incident to the handling of delinquent  payments,  but are in addition
to,  and  not in lieu  of,  the  Bank's  exercise  of any  rights  and  remedies
hereunder,  under the other Loan Documents or under applicable law, and any fees
and expenses of any agents or attorneys which the Bank may employ.  In addition,
the Default Rate  reflects the  increased  credit risk to the Bank of carrying a
loan that is in default.  The  Borrower  agrees that the Late Charge and Default
Rate are reasonable  forecasts of just  compensation  for anticipated and actual
harm incurred by the Bank,  and that the actual harm incurred by the Bank cannot
be estimated with certainty and without difficulty.

6. Prepayment.  The indebtedness  evidenced by this Note may be prepaid in whole
or in part at any time without penalty.

7. Yield  Protection.  The  Borrower  shall pay to the Bank,  on written  demand
therefor,  together with the written evidence of the justification therefor, all
direct costs incurred, losses suffered or payments made


                                      -3-
<PAGE>


by Bank by  reason  of any  change in law or  regulation  or its  interpretation
imposing any reserve,  deposit,  allocation of capital,  or similar  requirement
(including  without  limitation,  Regulation  D of the Board of Governors of the
Federal  Reserve  System)  on the  Bank,  its  holding  company  or any of their
respective  assets.  The Bank's  determination  of an amount  payable under this
paragraph  shall,  in the absence of manifest  error, be conclusive and shall be
payable on demand.

8.  Other  Loan  Documents.  This  Note is issued  in  connection  with a Letter
Agreement  between the Borrower and the Bank dated on or before the date hereof,
and the other  agreements  and  documents  executed in  connection  therewith or
referred to therein, the terms of which are incorporated herein by reference (as
amended,  modified  or  renewed  from  time  to  time,  collectively  the  "Loan
Documents"),  and is secured by the property described in the Loan Documents (if
any) and by such  other  collateral  as  previously  may have been or may in the
future be granted to the Bank to secure this Note.  All  capitalized  terms used
herein and not otherwise defined herein have the meanings given them in the Loan
Documents.

9. Events of Default.  The  occurrence  of any of the  following  events will be
deemed to be an "Event of Default"  under this Note:  (i) the  nonpayment of any
principal,  interest or other  indebtedness  under this Note within two (2) days
after the date when due; (ii) the  occurrence of any event of default or default
and the lapse of any notice or cure period under any Loan  Document or any other
debt, liability or obligation to the Bank of any Obligor; (iii) the filing by or
against any Obligor of any proceeding in bankruptcy,  receivership,  insolvency,
reorganization,  liquidation, conservatorship or similar proceeding (and, in the
case of any such proceeding  instituted against any Obligor,  such proceeding is
not dismissed or stayed  within 60 days of the  commencement  thereof,  provided
that the Bank shall not be  obligated  to advance  additional  funds during such
period); (iv) any assignment by any Obligor for the benefit of creditors, or any
levy,  garnishment,  attachment or similar  proceeding is instituted against any
property of any Obligor held by or deposited  with the Bank;  (v) a default with
respect  to any other  indebtedness  of any  Obligor in excess of  $250,000  for
borrowed  money,  if the  effect  of such  default  is to  cause or  permit  the
acceleration  of  such  debt;  (vi)  the  commencement  of  any  foreclosure  or
forfeiture  proceeding,  execution or attachment against any collateral securing
the obligations of any Obligor to the Bank; (vii) any material adverse change in
the business, assets,  operations,  financial condition or results of operations
of the Obligors, taken as a whole; (viii) the Obligors cease doing business as a
going concern; (ix) any change shall occur in the equity ownership of STV Group,
Incorporated which results in its current employee stock option plan owning less
than sixty percent (60%) of the voting control of STV Group,  Incorporated;  (x)
any  representation  or  warranty  made by any  Obligor  to the Bank in any Loan
Document, or any other documents now or in the future evidencing or securing the
obligations of any Obligor to the Bank, is false, erroneous or misleading in any
material adverse respect;  (xi) any Obligor's  failure to observe or perform any
of the Financial Reporting Covenants contained in Section A of Exhibit A to that
certain  Letter  Agreement  dated  February ___,  2000 (as amended,  modified or
renewed  from time to time,  the  "Letter  Agreement"),  or any of the  Negative
Covenants contained in Section C of Exhibit A to the Letter Agreement, provided,
however,  that if such failure is capable of being cured and  Borrower  promptly
undertakes to effect such cure,  such failure  shall not  constitute an Event of
Default  hereunder  unless it remains  uncured for a period of ten (10) days; or
(xii) any  Obligor's  failure  to  observe  or  perform  any  covenant  or other
agreement with the Bank  contained in any Loan Document  (other than as provided
in clause (xi) above) or any other documents now or in the future  evidencing or
securing the obligations of any Obligor to the Bank provided,  however,  that if
such  failure is capable of being  cured and  Borrower  promptly  undertakes  to
effect  such  cure,  such  failure  shall  not  constitute  an Event of  Default
hereunder  unless it remains  uncured for a period of thirty (30) days.  As used
herein, the term "Obligor" means any Borrower.


                                      -4-
<PAGE>


Upon  the  occurrence  of an Event of  Default:  (a) the Bank  shall be under no
further  obligation  to make  advances  hereunder;  (b) if an Event  of  Default
specified in clause (iii) or (iv) above shall occur,  the outstanding  principal
balance and accrued  interest  hereunder  together with any  additional  amounts
payable  hereunder shall be immediately due and payable without demand or notice
of any kind;  (c) if any other Event of Default  shall  occur,  the  outstanding
principal  balance and accrued interest  hereunder  together with any additional
amounts payable hereunder,  at the Bank's option and without demand or notice of
any kind, may be accelerated and become immediately due and payable;  (d) at the
Bank's option, this Note will bear interest at the Default Rate from the date of
the occurrence of the Event of Default;  and (e) the Bank may exercise from time
to time any of the rights and  remedies  available  under the Loan  Documents or
under applicable law.

10. Right of Setoff.  In addition to all liens upon and rights of setoff against
the Borrower's money, securities or other property given to the Bank by law, the
Bank shall have,  with respect to the  Borrower's  obligations to the Bank under
this Note and to the extent permitted by law, a contractual  possessory security
interest in and a contractual  right of setoff against,  and the Borrower hereby
assigns,  conveys,  delivers,  pledges  and  transfers  to the  Bank  all of the
Borrower's right, title and interest in and to, all of the Borrower's  deposits,
moneys,  securities  and other property now or hereafter in the possession of or
on deposit  with,  or in transit  to, the Bank or any other  direct or  indirect
subsidiary  of PNC Bank Corp.,  whether held in a general or special  account or
deposit, whether held jointly with someone else, or whether held for safekeeping
or otherwise, excluding, however, all IRA, Keogh, and trust accounts. Every such
security  interest and right of setoff may be exercised  without  demand upon or
notice to the Borrower.  Every such right of setoff shall be deemed to have been
exercised  immediately  upon the  occurrence  of an Event of  Default  hereunder
without any action of the Bank,  although  the Bank may enter such setoff on its
books and records at a later time.

11. Miscellaneous. All notices, demands, requests, consents, approvals and other
communications required or permitted hereunder must be in writing (except as may
be agreed  otherwise  above with  respect  to  borrowing  requests)  and will be
effective  upon  receipt.   Such  notices  and  other   communications   may  be
hand-delivered, sent by facsimile transmission with confirmation of delivery and
a copy sent by  first-class  mail,  or sent by nationally  recognized  overnight
courier service,  to the addresses for the Bank and the Borrower set forth above
or to such other  address  as either  may give to the other in writing  for such
purpose.  No delay or omission on the Bank's part to exercise any right or power
arising  hereunder will impair any such right or power or be considered a waiver
of any such right or power,  nor will the Bank's  action or inaction  impair any
such right or power.  No  modification,  amendment or waiver of any provision of
this  Note nor  consent  to any  departure  by the  Borrower  therefrom  will be
effective  unless made in a writing signed by the Bank.  The Borrower  agrees to
pay on demand, to the extent permitted by law, all reasonable costs and expenses
incurred  by the Bank in the  enforcement  of its rights in this Note and in any
security therefor,  including without limitation reasonable fees and expenses of
the Bank's  counsel.  If any  provision of this Note is found to be invalid by a
court,  all the other  provisions  of this Note  will  remain in full  force and
effect.  The  Borrower  and all other  makers and  indorsers of this Note hereby
forever  waive   presentment,   protest,   notice  of  dishonor  and  notice  of
non-payment.  The  Borrower  also waives all  defenses  based on  suretyship  or
impairment  of  collateral.  If this Note is executed by more than one Borrower,
the obligations of such persons or entities hereunder will be joint and several.
This Note  shall bind the  Borrower  and its  successors  and  assigns,  and the
benefits  hereof shall inure to the benefit of the Bank and its  successors  and
assigns; provided,  however, that the Borrower may not assign this Note in whole
or in part  without  the  Bank's  written  consent  and the Bank at any time may
assign this Note in whole or in part.


                                      -5-
<PAGE>


This Note has been  delivered  to and accepted by the Bank and will be deemed to
be made in the Commonwealth of  Pennsylvania.  THIS NOTE WILL BE INTERPRETED AND
THE RIGHTS AND LIABILITIES OF THE BANK AND THE BORROWER DETERMINED IN ACCORDANCE
WITH THE LAWS OF THE  COMMONWEALTH  OF  PENNSYLVANIA,  EXCLUDING ITS CONFLICT OF
LAWS  RULES.  The  Borrower  hereby   irrevocably   consents  to  the  exclusive
jurisdiction  of any state or federal  court in the county or judicial  district
where the Bank's  office  indicated  above is  located;  provided  that  nothing
contained in this Note will prevent the Bank from bringing any action, enforcing
any  award  or  judgment  or   exercising   any  rights   against  the  Borrower
individually,  against  any  security or against  any  property of the  Borrower
within any other county,  state or other foreign or domestic  jurisdiction.  The
Borrower  acknowledges  and  agrees  that the venue  provided  above is the most
convenient  forum for both the Bank and the  Borrower.  The Borrower  waives any
objection to venue and any  objection  based on a more  convenient  forum in any
action instituted under this Note.

12. WAIVER OF JURY TRIAL. THE BORROWER IRREVOCABLY WAIVES ANY AND ALL RIGHTS THE
BORROWER MAY HAVE TO A TRIAL BY JURY IN ANY ACTION,  PROCEEDING  OR CLAIM OF ANY
NATURE  RELATING TO THIS NOTE,  ANY DOCUMENTS  EXECUTED IN CONNECTION  WITH THIS
NOTE OR ANY  TRANSACTION  CONTEMPLATED  IN ANY OF SUCH  DOCUMENTS.  THE BORROWER
ACKNOWLEDGES THAT THE FOREGOING WAIVER IS KNOWING AND VOLUNTARY.

The Borrower  acknowledges that it has read and understood all the provisions of
this Note,  including the waiver of jury trial,  and has been advised by counsel
as necessary or appropriate.


WITNESS the due execution  hereof as a document under seal, as of the date first
written above, with the intent to be legally bound hereby.

WITNESS/ATTEST:                                STV GROUP, INCORPORATED

/s/ Lori Jo Berk                               By:  /s/ Peter W. Knipe    (SEAL)
Print Name:  Lori Jo Berk                      Print Name:  Peter W. Knipe
Title:  Admin. Asst.                           Title:  CFO


WITNESS/ATTEST:                                STV INCORPORATED

/s/ Lori Jo Berk                               By:  /s/ Peter W. Knipe    (SEAL)
Print Name:  Lori Jo Berk                      Print Name:  Peter W. Knipe
Title:  Admin. Asst.                           Title:  CFO



                [SIGNATURES ARE CONTINUED ON THE FOLLOWING PAGE]


                                      -6-
<PAGE>


WITNESS/ATTEST:                                STV CONSTRUCTION SERVICES, INC.

/s/ Lori Jo Berk                               By:  /s/ Peter W. Knipe    (SEAL)
Print Name:  Lori Jo Berk                      Print Name:  Peter W. Knipe
Title:  Admin. Asst.                           Title:  CFO


WITNESS/ATTEST:                                STV INTERNATIONAL, INC.

/s/ Lori Jo Berk                               By:  /s/ Peter W. Knipe    (SEAL)
Print Name:  Lori Jo Berk                      Print Name:  Peter W. Knipe
Title:  Admin. Asst.                           Title:  CFO


WITNESS/ATTEST:                                STV/ENVIRONMENTAL, INC.

/s/ Lori Jo Berk                               By:  /s/ Peter W. Knipe    (SEAL)
Print Name:  Lori Jo Berk                      Print Name:  Peter W. Knipe
Title:  Admin. Asst.                           Title:  CFO


WITNESS/ATTEST:                                STV SURVEYING, INC.

/s/ Lori Jo Berk                               By:  /s/ Peter W. Knipe    (SEAL)
Print Name:  Lori Jo Berk                      Print Name:  Peter W. Knipe
Title:  Admin. Asst.                           Title:  CFO


WITNESS/ATTEST:                                STV CONSTRUCTION, INC.

/s/ Lori Jo Berk                               By:  /s/ Peter W. Knipe    (SEAL)
Print Name:  Lori Jo Berk                      Print Name:  Peter W. Knipe
Title:  Admin. Asst.                           Title:  CFO


WITNESS/ATTEST:                                STV ARCHITECTS, INC.

/s/ Lori Jo Berk                               By:  /s/ Peter W. Knipe    (SEAL)
Print Name:  Lori Jo Berk                      Print Name:  Peter W. Knipe
Title:  Admin. Asst.                           Title:  Secretary



                [SIGNATURES ARE CONTINUED ON THE FOLLOWING PAGE]


                                      -7-
<PAGE>


WITNESS/ATTEST:                                STV SILVER & ZISKIND ARCHITECTS,
                                               P.C.

/s/ Lori Jo Berk                               By:  /s/ Peter W. Knipe    (SEAL)
Print Name:  Lori Jo Berk                      Print Name:  Peter W. Knipe
Title:  Admin. Asst.                           Title:  Secretary


WITNESS/ATTEST:                                STV ARCHITECTS, P.C.

/s/ Lori Jo Berk                               By:  /s/ Michael D. Garz   (SEAL)
Print Name:  Lori Jo Berk                      Print Name:  Michael D. Garz
Title:  Admin. Asst.                           Title:  President



                                      -8-