EXHIBIT 10.1
------------


                      FIRST AMENDMENT TO CREDIT AGREEMENT

      This FIRST AMENDMENT TO CREDIT AGREEMENT (this "Agreement"), dated as
of March 25, 2005, is between LANDAUER, INC., a Delaware corporation
("Borrower"); HOMEBUYER'S PREFERRED, INC., an Illinois corporation
("Homebuyer's Preferred"), HEALTHY HOME AIR, INC., a Delaware corporation
("Healthy Home"), and LANDAUER INTERNATIONAL LLC, a Delaware limited
liability company ("Landauer International") (Homebuyer's Preferred,
Healthy Home and Landauer International sometimes hereinafter are referred
to as each "Guarantor" and collectively as the "Guarantors"); and LASALLE
BANK NATIONAL ASSOCIATION, a national banking association ("Bank").


                               R E C I T A L S:
                               ---------------

      A.     Borrower and Bank entered into that certain Credit Agreement
dated as of April 13, 2004 (the "Credit Agreement"), pursuant and subject
to the terms and conditions of which Bank agreed to make loans and other
financial accommodations to Borrower.

      B.     Each Guarantor is a Subsidiary of Borrower.  Each Guarantor
guaranteed Borrower's Obligations pursuant to that certain Guaranty dated
as of April 13, 2004 made by Guarantors in favor of Bank.

      C.     Borrower and Guarantors have requested that Bank (i) extend the
Maturity Date to March 25, 2006, (ii) reduce the Revolving Loan Commitment
to $15,000,000, (iii) alter the definition of "Interest Period" to permit
overnight and one week EURIBO Loans and LIBOR Loans, (iv) provide a
mechanism whereby Borrower may request an increase in the Revolving Loan
Commitment to $25,000,000 and (v) increase the minimum tangible net worth
covenant to $19,876,000.

      D.     Bank is willing to agree to the requests of Borrower and
Guarantors on the terms and conditions set forth herein.

      NOW, THEREFORE, in consideration of the mutual agreements contained
herein, and for other good and valuable consideration, the receipt and
sufficiency of which hereby are acknowledged, Borrower, Guarantors and Bank
agree as follows:

      1.     INCORPORATION OF RECITALS.  The Recitals set forth above are
incorporated herein, are acknowledged by Borrower and Guarantors to be true
and correct and by this reference are made a part hereof.

      2.     DEFINITIONS.  All capitalized terms used but not elsewhere
defined herein shall have the respective meanings ascribed to such terms in
the Credit Agreement, as amended by this Agreement.

      3.     AMENDMENTS TO CREDIT AGREEMENT.  The Credit Agreement is
amended as set forth below:

             (a)   SECTION 1.1 - AMENDED DEFINITIONS.  Section 1.1 of the
      Credit Agreement is amended by deleting the current version of the
      following definitions in their entirety and substituting the
      following versions:

                   "INTEREST PERIOD:  means a period (i) commencing (A) on
             the applicable Funding Date, if Borrower prior thereto has
             elected pursuant to subsection 2.5.1 to have all or a portion
             of the Advance to be disbursed on such date bear interest from
             such date at a LIBO Rate or a EURIBO Rate, (B) with respect to




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             the conversion of a Base Rate Loan to a LIBOR Loan, on the
             Business Day specified by Borrower in the applicable LIBOR
             Election Notice, (C) with respect to the redenomination of a
             Base Rate Loan into Euros and the conversion of such Base Rate
             Loan to a Euro Loan, on the Business Day specified by Borrower
             in the applicable EURIBOR Election Notice and (D) with respect
             to the continuation as a LIBOR Loan or a Euro Loan of all or a
             portion of a then existing LIBOR Loan or Euro Loan after the
             expiration of the Interest Period applicable to such existing
             LIBOR Loan or Euro Loan, on the last day of the Interest Period
             applicable to such existing LIBOR Loan or Euro Loan, and (ii)
             ending one day, one week or one, two, three or six months
             thereafter, as selected by Borrower in its LIBOR Election
             Notice or EURIBOR Election Notice; provided, however:

                         (a)   if any Interest Period otherwise would end on
                   a day that is not a Business Day, such Interest Period
                   shall end on the next succeeding Business Day, unless the
                   result of such extension would be to carry such Interest
                   Period into another calendar month, in which event such
                   Interest Period shall end on the immediately preceding
                   Business Day;

                         (b)   any Interest Period that begins on a day for
                   which there is no numerically corresponding day in the
                   last month of such Interest Period shall end on the last
                   Business Day of the last month of such Interest Period;

                         (c)   Interest Periods for LIBOR Loans and Euro
                   Loans disbursed on the same date shall be of the same
                   duration; and

                         (d)   Borrower may not select any Interest Period
                   that ends after the Maturity Date.

                   MATURITY DATE:  means the earlier of (i) March 25, 2006
             or (ii) the date on which Borrower's Obligations are
             accelerated pursuant to this Credit Agreement.

                   REVOLVING LOAN COMMITMENT:  means Fifteen Million Dollars
             ($15,000,000), as such amount may be increased to an amount not
             in excess of Twenty-Five Million Dollars ($25,000,000) as a
             result of New Revolving Loan Commitments accepted by Bank
             pursuant to subsection 2.1.2

             (b)   SECTION 1.1 - ADDITIONAL DEFINITIONS.  Section 1.1 of the
      Credit Agreement is amended by inserting the following definitions in
      appropriate alphabetical order:

                   COMMITMENT INCREASE NOTICE:  has the meaning ascribed
             thereto in subsection 2.1.2.

                   INCREASED REVOLVING LOAN AMOUNT DATE:  has the meaning
             ascribed thereto in subsection 2.1.2.

                   NEW BANK:  has the meaning ascribed thereto in subsection
             2.1.2.

                   NEW REVOLVING LOAN:  has the meaning ascribed thereto in
             subsection 2.1.2.

                   NEW REVOLVING LOAN COMMITMENT:  has the meaning ascribed
             thereto in subsection 2.1.2.







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<PAGE>


             (c)   SECTION 2.1 - REVOLVING LOAN.  Section 2.1 of the Credit
      Agreement is amended by renumbering the existing Section 2.1 as
      subsection 2.1.1 and inserting the following thereafter as subsection
      2.1.2:

             "2.1.2      NEW REVOLVING LOANS.

                   (a)   Subject to the terms and conditions of this
             subsection 2.1.2, at any time and from time to time but prior
             to the Maturity Date, by written notice (each, a "Commitment
             Increase Notice") to Bank, Borrower may elect to request an
             increase in the aggregate amount of the existing Revolving Loan
             Commitment (any such increase, the "New Revolving Loan
             Commitment") by an amount not in excess of $10,000,000 in the
             aggregate and not less than $1,000,000 in any individual
             request (or such lesser amount which shall be approved by Bank
             or such lesser amount that shall constitute the difference
             between $10,000,000 and all such New Revolving Loan Commitments
             obtained prior to such date) and integral multiples of
             $1,000,000 in excess of that amount.  Each Commitment Increase
             Notice shall specify (i) the date (each, an "Increased
             Revolving Loan Amount Date") on which Borrower proposes that
             the New Revolving Loan Commitment shall be effective, which
             shall be a date not less than (A) ten (10) Business Days after
             the date on which such Commitment Increase Notice is delivered
             to Bank if Bank agrees to provide such New Revolving Loan
             Commitment and (ii) twenty (20) Business Days after the date on
             which such Commitment Increase Notice is delivered to Bank if
             Bank declines to provide such New Revolving Loan Commitment and
             one or more financial institutions other than Bank (each, a
             "New Bank") agree to provide such New Revolving Loan Commitment
             and (ii) the identity of each New Bank to whom Borrower
             proposes any portion of such New Revolving Loan Commitments, as
             applicable, be allocated and the amounts of such allocations.
             Borrower first shall offer the New Revolving Loan Commitment to
             Bank and Borrower shall accept any New Revolving Loan
             Commitment which Bank elects to provide.  Bank and each New
             Bank may elect or decline, in its sole discretion, to provide a
             New Revolving Loan Commitment.  In the event Bank declines to
             provide all or any portion of such New Revolving Loan
             Commitment, Bank shall have approved each New Bank which is to
             provide a New Revolving Loan Commitment.  In the event of any
             oversubscription for any New Revolving Loan Commitment Bank
             shall determine the final allocation amounts.  Such New
             Revolving Loan Commitment shall become effective as of such
             Increased Revolving Loan Amount Date; PROVIDED THAT (1) no
             Incipient Default or Event of Default shall exist on such
             Increased Revolving Loan Amount Date before or after giving
             effect to such New Revolving Loan Commitment; (2) Bank and each
             New Bank, if any, has delivered to Borrower its written
             acceptance of such New Revolving Loan Commitment; (3) in the
             event Bank declines to provide all or any portion of such New
             Revolving Loan Commitment and one or more New Banks have agreed
             to provide such New Revolving Loan Commitment, Bank, Borrower
             and each New Bank shall have entered into an amended and
             restated credit agreement in form and substance satisfactory to
             each of Bank, Borrower and each New Bank amending and restating
             this Credit Agreement in its entirety; and (4) Borrower shall
             have delivered or caused to be delivered any legal opinions or
             other documents reasonably requested by Bank in connection with
             any such transaction.

                   (b)   Effective upon any Increased Revolving Loan Amount
             Date, each New Revolving Loan Commitment shall be deemed for
             all purposes a Revolving Loan Commitment and each Advance made
             thereunder (a "New Revolving Loan") shall be deemed, for all
             purposes, a Revolving Loan.



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<PAGE>


                   (c)   The terms, provisions and interest rate of the New
             Revolving Loans shall be identical to the Revolving Loans."

             (d)   SECTION 6.10 - MINIMUM TANGIBLE NET WORTH.  Section 6.10
      of the Credit Agreement is deleted in its entirety and the following
      is substituted in lieu thereof:

                   "6.10 MINIMUM TANGIBLE NET WORTH.  Borrower shall not
             permit Tangible Net Worth to be less than $19,876,000 at the
             end of any Fiscal Quarter."

             (e)   EXHIBITS.  Exhibits 1.1(B) and 1.1(C) attached to the
      Credit Agreement are deleted in their entirety and Exhibits 1.1(B)
      and 1.1(C) attached hereto are substituted in lieu thereof:

      4.     CONDITIONS TO EFFECTIVENESS.  The effectiveness of this
Agreement shall be subject to the satisfaction of all of the following
conditions in a manner, form and substance satisfactory to Bank:

             (a)   DELIVERY OF DOCUMENTS.  The following shall have
      been delivered to Bank, each duly authorized and executed and each in
      form and substance satisfactory to Bank:

                   (1)   this Agreement; and

                   (2)   such other instruments, documents, certificates,
             consents, waivers and opinions as Bank reasonably may request.

             (b)   NO DEFAULT.  No Event of Default or Incipient Default
      shall exist.

             (c)   MATERIAL ADVERSE EFFECT.  No event shall have occurred
      since December 31, 2004 which has had or could have a material
      adverse effect on the financial condition or affairs of Borrower.

      The date on which all of the conditions set forth in this Section 6
have been satisfied is referred to herein as the "Effective Date."

      5.     REFERENCES.  From and after the Effective Date hereof, all
terms used in the Credit Documents which are defined in the Credit
Agreement shall be deemed to refer to such terms as amended by this
Agreement.  This Agreement shall constitute a "Credit Document."

      6.     REPRESENTATIONS AND WARRANTIES.  Borrower and each Guarantor
hereby confirms to Bank that the representations and warranties set forth
in the Credit Documents are true and correct in all material respects as of
the date hereof (unless any such representation or warranty relates to a
specific date, in which case such representation or warranty is true and
correct as of such date), and shall be deemed to be remade as of the date
hereof (unless any such representation or warranty relates to a specific
date, in which case such representation or warranty shall be deemed to be
remade as of such date).  Borrower and each Guarantor represents and
warrants to Bank that (i) it has full power and authority to execute and
deliver this Agreement and to perform its obligations hereunder, (ii) upon
the execution and delivery hereof, this Agreement will be valid, binding
and enforceable upon it in accordance with its terms (except as such
enforceability may be limited by (x) applicable bankruptcy, insolvency,
reorganization, moratorium or similar laws now or hereafter in effect
affecting the enforcement of creditors' rights generally and (y) equitable
principles (whether or not any action to enforce this Agreement is brought
at law or in equity), (iii) the execution and delivery of this Agreement
does not and will not contravene, conflict with, violate or constitute a
default under (A) its articles or certificate of incorporation, by-laws,
certificate of formation or operating agreement, as applicable, or (B) any
applicable law, rule, regulation, judgment, decree or order or any
agreement, indenture or instrument to which it is a party or is bound or
which is binding upon or applicable to all or any portion of its Property
and (iv) as of the date hereof no Event of Default exists.


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<PAGE>


      7.     NO FURTHER AMENDMENTS; RATIFICATION OF LIABILITY.  Except as
amended hereby, the Credit Agreement and each of the other Credit Documents
shall remain in full force and effect in accordance with their respective
terms.  Borrower and each Guarantor hereby ratifies and confirms its
liabilities, obligations and agreements under the Credit Agreement and the
other Credit Documents, all as amended by this Agreement, and the Liens
created thereby, and acknowledges that (i) it has no defenses, claims or
set-offs to the enforcement by Bank of such liabilities, obligations and
agreements, (ii) Bank has fully performed all obligations to Borrower and
Guarantors which it may have had or has on and as of the date hereof and
(iii) other than as specifically set forth herein, Bank does not waive,
diminish or limit any term or condition contained in the Credit Agreement
or the other Credit Documents.  The Credit Documents, as amended by this
Agreement, contain the entire agreement between Bank, Borrower and
Guarantors with respect to the transactions contemplated hereby.

      8.     RELEASE OF CLAIMS.  In consideration of the execution and
delivery of this Agreement by Bank, the sufficiency of which is
acknowledged, and excepting only the contractual obligations respecting
future performance by Bank arising under the Credit Agreement and the other
Credit Documents, Borrower and each Guarantor hereby irrevocably releases
and forever discharges Bank and each of its affiliates, subsidiaries,
successors, assigns, directors, officers, employees, agents,
representatives and attorneys (each, a "Released Person") of and from all
damages, losses, claims, demands, liabilities, obligations, actions and
causes of action whatsoever which Borrower or such Guarantor may now have
or claim to have on and as of the date hereof against any Released Person,
whether presently known or unknown, liquidated or unliquidated, suspected
or unsuspected, contingent or non-contingent, and of every nature and
extent whatsoever (collectively, "Claims").  Borrower and each Guarantor
represents and warrants to Bank that it has not granted or purported to
grant to any other Person any interest whatsoever in any Claim, as security
or otherwise.  Borrower and each Guarantor shall indemnify, defend and hold
harmless each Released Person from and against any and all Claims and any
loss, cost, liability, damage or expense (including reasonable attorneys'
fees and expenses) incurred by any Released Person in investigating,
preparing for, defending against, providing evidence or producing documents
in connection with or taking other action in respect of any commenced or
threatened Claim.

      9.     COUNTERPARTS.  This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original, and all of which,
when taken together, shall constitute one and the same instrument.

      10.    FURTHER ASSURANCES.  Borrower and each Guarantor covenants and
agrees that it will at any time and from time to time do, execute,
acknowledge and deliver, or will cause to be done, executed, acknowledged
and delivered, all such further acts, documents and instruments as
reasonably may be required by Bank in order to effectuate fully the intent
of this Agreement.

      11.    SEVERABILITY.  If any term or provision of this Agreement or
the application thereof to any party or circumstance shall be held to be
invalid, illegal or unenforceable in any respect by a court of competent
jurisdiction, the validity, legality and enforceability of the remaining
terms and provisions of this Agreement shall not in any way be affected or
impaired thereby, and the affected term or provision shall be modified to
the minimum extent permitted by law so as most fully to achieve the
intention of this Agreement.

      12.    CAPTIONS.  The captions in this Agreement are inserted for
convenience of reference only and in no way define, describe or limit the
scope or intent of this Agreement or any of the provisions hereof.

      13.    ENTIRE AGREEMENT.  This Agreement, the Credit Agreement and the
other Credit Documents executed prior or pursuant hereto constitute the
entire agreement among the parties hereto with respect to the transactions
contemplated hereby or thereby and supersede any prior agreements, whether
written or oral, relating to the subject matter hereof.

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<PAGE>


      14.    APPLICABLE LAW.  THIS AGREEMENT AND THE OTHER CREDIT DOCUMENTS
SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY THE LAWS AND
DECISIONS OF THE STATE OF ILLINOIS, WITHOUT REGARD TO CONFLICT OF LAWS
PRINCIPLES.

      15.    JURISDICTION AND VENUE.  BORROWER AND EACH GUARANTOR HEREBY
AGREES THAT ALL ACTIONS OR PROCEEDINGS INITIATED BY BORROWER OR SUCH
GUARANTOR AND ARISING DIRECTLY OR INDIRECTLY OUT OF THIS AGREEMENT OR ANY
OTHER CREDIT DOCUMENT SHALL BE LITIGATED EITHER IN THE CIRCUIT COURT OF
COOK COUNTY, ILLINOIS OR IN THE UNITED STATES DISTRICT COURT FOR THE
NORTHERN DISTRICT OF ILLINOIS, OR IF BANK INITIATES SUCH ACTION, IN
ADDITION TO THE FOREGOING COURTS, ANY COURT IN WHICH BANK SHALL INITIATE OR
TO WHICH BANK SHALL REMOVE SUCH ACTION, TO THE EXTENT SUCH COURT HAS
JURISDICTION.  BORROWER AND EACH GUARANTOR HEREBY EXPRESSLY SUBMITS AND
CONSENT IN ADVANCE TO SUCH JURISDICTION IN ANY ACTION OR PROCEEDING
COMMENCED BY BANK IN OR REMOVED BY BANK TO ANY OF SUCH COURTS, AND HEREBY
AGREES THAT PERSONAL SERVICE OF THE SUMMONS AND COMPLAINT, OR OTHER PROCESS
OR PAPERS ISSUED THEREIN MAY BE MADE BY REGISTERED OR CERTIFIED MAIL
ADDRESSED TO BORROWER AT THE ADDRESS TO WHICH NOTICES ARE TO BE SENT
PURSUANT TO SECTION 11.1 OF THE CREDIT AGREEMENT.  BORROWER AND EACH
GUARANTOR WAIVES ANY CLAIM THAT THE CIRCUIT COURT OF COOK COUNTY, ILLINOIS
OR THE UNITED STATES DISTRICT COURT FOR THE NORTHERN DISTRICT OF ILLINOIS
IS AN INCONVENIENT FORUM OR AN IMPROPER FORUM BASED ON LACK OF VENUE.  THE
EXCLUSIVE CHOICE OF FORUM FOR BORROWER AND EACH GUARANTOR SET FORTH IN THIS
SECTION 15 SHALL NOT BE DEEMED TO PRECLUDE THE ENFORCEMENT BY BANK OF ANY
JUDGMENT OBTAINED IN ANY OTHER FORUM OR THE TAKING BY BANK OF ANY ACTION TO
ENFORCE THE SAME IN ANY OTHER APPROPRIATE JURISDICTION, AND BORROWER AND
EACH GUARANTOR HEREBY WAIVES THE RIGHT TO COLLATERALLY ATTACK ANY SUCH
JUDGMENT OR ACTION.

      16.    WAIVER OF RIGHT TO JURY TRIAL.  BANK, BORROWER AND EACH
GUARANTOR ACKNOWLEDGE AND AGREE THAT ANY CONTROVERSY WHICH MAY ARISE UNDER
ANY OF THE CREDIT DOCUMENTS OR WITH RESPECT TO THE TRANSACTIONS
CONTEMPLATED THEREBY WOULD BE BASED UPON DIFFICULT AND COMPLEX ISSUES AND,
THEREFORE, THE PARTIES AGREE THAT ANY LAWSUIT ARISING OUT OF ANY SUCH
CONTROVERSY WILL BE TRIED IN A COURT OF COMPETENT JURISDICTION BY A JUDGE
SITTING WITHOUT A JURY.



   [remainder of this page intentionally left blank; signature page follows]





























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<PAGE>


      IN WITNESS WHEREOF, this Agreement has been executed and delivered by
each of the parties hereto by a duly authorized officer of each such party
on the date first set forth above.


                               LANDAUER, INC., a Delaware corporation


                               By:      /s/ James M. O'Connell
                                        ------------------------------
                               Name:    James M. O'Connell
                               Title:   Vice President and Treasurer



                               HOMEBUYER'S PREFERRED, INC.,
                               an Illinois corporation


                               By:      /s/ James M. O'Connell
                                        ------------------------------
                               Name:    James M. O'Connell
                               Title:   Treasurer



                               HEALTHY HOME AIR, INC.,
                               a Delaware corporation


                               By:      /s/ James M. O'Connell
                                        ------------------------------
                               Name:    James M. O'Connell
                               Title:   Treasurer



                               LANDAUER INTERNATIONAL LLC,
                               a Delaware limited liability company


                               By:      /s/ James M. O'Connell
                                        ------------------------------
                               Name:    James M. O'Connell
                               Title:   Manager



                               LASALLE BANK NATIONAL ASSOCIATION,
                               a national banking association


                               By:      /s/ Scott M. Carbon
                               Name:    Scott M. Carbon
                                        ------------------------------
                               Title:   Vice President














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<PAGE>


                                Exhibit 1.1(B)

                        Form of EURIBOR Election Notice

                                (See Attached)





<PAGE>


                            EURIBOR ELECTION NOTICE

                                LANDAUER, INC.

                               ___________, ____



LaSalle Bank National Association
135 South LaSalle Street
Chicago, Illinois  60603
Attention: Scott Carbon


Ladies and Gentlemen:

      Reference is made to the Credit Agreement dated as of April 13, 2004
(as amended, the "Credit Agreement") between the undersigned, Landauer,
Inc., and LaSalle Bank National Association.  Capitalized terms used but
not elsewhere defined herein shall have the respective meanings ascribed to
such terms in the Credit Agreement.

      Borrower hereby irrevocably requests that Bank:

      .      disburse as a Euro Loan, on _______________, _____, the
             Equivalent in Euros of $__________ of the Advance being
             requested pursuant to the Notice of Borrowing of even date
             herewith for an interest period of [one day] [one week]
             [__________ months];

      .      continue as a Euro Loan, on _______________, _____, the
             Euro Loan in the Equivalent in Euros of $__________ now
             bearing interest determined by reference to a EURIBO Rate
             for an additional interest period of [one day] [one week]
             [__________ months];

      .      redenominate to Euros, on _______________, _____, $_________
             of the Principal Balance now bearing interest determined
             by reference to the Base Rate, such Euro Loan to bear
             interest determined by reference to the EURIBO Rate for
             an interest period of [one day] [one week] [__________ months].



                               LANDAUER, INC., a Delaware corporation


                               By:
                                        ------------------------------

                               Name:
                                        ------------------------------

                               Title:
                                        ------------------------------





<PAGE>


                                Exhibit 1.1(C)

                         Form of LIBOR Election Notice

                                (See Attached)





<PAGE>


                             LIBOR ELECTION NOTICE

                                LANDAUER, INC.
                               ___________, ____


LaSalle Bank National Association
135 South LaSalle Street
Chicago, Illinois  60603
Attention: Scott Carbon


Ladies and Gentlemen:

      Reference is made to the Credit Agreement dated as of April 13, 2004
(as amended, the "Credit Agreement") between the undersigned, Landauer,
Inc., and LaSalle Bank National Association.  Capitalized terms used but
not elsewhere defined herein shall have the respective meanings ascribed to
such terms in the Credit Agreement.

      Borrower hereby irrevocably requests that Bank:

      .      disburse as a LIBOR Loan, on _______________, _____,
             $__________ of the Advance being requested pursuant to the
             Notice of Borrowing of even date herewith for an interest
             period of [one day] [one week] [__________ months];

      .      continue as a LIBOR Loan, on _______________, _____, the
             $__________ LIBOR Loan now bearing interest determined by
             reference to a LIBO Rate for an additional interest period of
             [one day] [one week] [__________ months];

      .      convert to a LIBOR Loan, on _______________, _____, $__________
             of the $__________ portion of the Principal Balance now bearing
             determined by reference to the Base Rate, such LIBOR Loan to
             bear interest determined by reference to the LIBO Rate for an
             interest period of[one day] [one week] [__________ months].



                               LANDAUER, INC., a Delaware corporation


                               By:
                                        ------------------------------

                               Name:
                                        ------------------------------

                               Title:
                                        ------------------------------