exhibit4b.htm


    EXHIBIT
4(b)

    


    


    


    
      


    

    


    


    


    


    


    PUBLIC
SERVICE COMPANY OF OKLAHOMA

    


    


    and

    


    


    THE BANK
OF NEW YORK,

    AS
TRUSTEE

    


    


    ___________________

    


    


    SIXTH
SUPPLEMENTAL INDENTURE

    


    Dated as
of August 10, 2006

    


    


    Supplemental
to the Indenture

    dated as
of November 1, 2000

    


    


    6.15%
Senior Notes, Series F, due 2016

    
      


      


      


      
        
          
          

        

        
          
          

          
            

          

        

        
          
          

        

      

      


      


    

    


    


    


    


    


    SIXTH SUPPLEMENTAL INDENTURE, dated as
of August 10, 2006, between PUBLIC SERVICE COMPANY OF OKLAHOMA, a corporation
duly organized and existing under the laws of the State of Oklahoma (the
“Company”), and THE BANK OF NEW YORK, a New York banking corporation organized
and existing under the laws of the State of New York, as Trustee under the
Original Indenture referred to below (the “Trustee”).

    


    RECITALS
OF THE COMPANY

    


    The Company has heretofore executed and
delivered to the Trustee an indenture dated as of November 1, 2000 (the
“Original Indenture”), to provide for the issuance from time to time of its
debentures, notes or other evidences of indebtedness (the “Senior Notes”), the
form and terms of which are to be established as set forth in Section 201 and
301 of the Original Indenture.

    


    Section 901 of the Original Indenture
provides, among other things, that the Company and the Trustee may enter into
indentures supplemental to the Original Indenture for, among other things, the
purpose of establishing the form and terms of the Senior Notes of any series as
permitted in Sections 201 and 301 of the Original Indenture.

    


    The Company desires to create a series
of the Senior Notes in an aggregate principal amount of $150,000,000 to be
designated the “6.15% Senior Notes, Series F, due 2016” (the “6.15% Senior
Notes”), and all action on the part of the Company necessary to authorize the
issuance of the 6.15% Senior Notes under the Original Indenture and this Sixth
Supplemental Indenture has been duly taken.

    


    All acts and things necessary to make
the 6.15% Senior Notes, when executed by the Company and completed,
authenticated and delivered by the Trustee as provided in the Original Indenture
and this Sixth Supplemental Indenture, the valid and binding obligations of the
Company and to constitute these presents a valid and binding supplemental
indenture and agreement according to its terms, have been done and
performed.

    


    NOW,
THEREFORE, THIS SIXTH SUPPLEMENTAL INDENTURE WITNESSETH:

    


    That in
consideration of the premises and of the acceptance and purchase of the 6.15%
Senior Notes by the Holders thereof and of the acceptance of this trust by the
Trustee, the Company covenants and agrees with the Trustee, for the equal
benefit of the Holders of the 6.15% Senior Notes, as follows:

    


    ARTICLE
ONE

    Definitions

    


               The
use of the terms and expressions herein is in accordance with the definitions,
uses and constructions contained in the Original Indenture and the form of the
Global Security attached hereto as Exhibit
A.

    


    


    ARTICLE
TWO

    Terms and
Issuance of the 6.15% Senior Notes

    


    SECTION
201.                                Issue of 6.15% Senior
Notes

    


    A series of Senior Notes which shall be
designated the “6.15% Senior Notes, Series F, due 2016” shall be executed,
authenticated and delivered from time to time in accordance with the provisions
of, and shall in all respects be subject to, the terms, conditions and covenants
of, the Original Indenture and this Sixth Supplemental Indenture (including the
form of Global Security set forth in Exhibit A
hereto).  The aggregate principal amount of the 6.15% Senior Notes,
which may be authenticated and delivered under this Sixth Supplemental Indenture
shall initially be $150,000,000, and such principal amount of the 6.15% Senior
Notes may be increased from time to time.  All 6.15% Senior Notes need
not be issued at the same time and such series may be reopened at any time,
without the consent of any Holder, for issuance of additional 6.15% Senior
Notes.  Any such additional 6.15% Senior Notes will have the same
interest rate, maturity and other terms as those initially issued.

    


    SECTION
202.                                Form of 6.15% Senior Notes,
Incorporation of Terms

    


    The 6.15% Senior Notes shall be
substantially in the form of the Global Security attached hereto as Exhibit
A.  The terms of such 6.15% Senior Notes are herein
incorporated by reference and are part of this Sixth Supplemental
Indenture.

    


    SECTION
203.                                Depositary for Global
Securities

    


    The Depositary for any Global
Securities of the series of which this 6.15% Senior Note is a part shall be The
Depository Trust Company in The City of New York.

    


    SECTION
204.                                Restrictions on
Liens

    


    The covenant contained in Section 1007
of the Original Indenture shall not be applicable to the 6.15% Senior
Notes.

    


    So long
as any of the 6.15% Senior Notes are outstanding, the Company will not create or
suffer to be created or to exist any additional mortgage, pledge, security
interest, or other lien (collectively “Liens”) on any of its utility properties
or tangible assets now owned or hereafter acquired to secure any indebtedness
for borrowed money (“Secured Debt”), without providing that the 6.15% Senior
Notes will be similarly secured.  This restriction does not apply to
the Company’s subsidiaries, nor will it prevent any of them from creating or
permitting to exist Liens on their property or assets to secure any Secured
Debt.  Further, this restriction on Secured Debt does not apply to the
Company’s existing first mortgage bonds that have previously been issued under
its Mortgage and Deed of Trust, dated July 1, 1945, between the Company and
Liberty Bank and Trust Company of Tulsa, National Association, as successor to
The First National Bank and Trust Company of Tulsa, now The Bank of New York, as
successor Trustee or any indenture supplemental thereto; provided that this
restriction will apply to future issuances thereunder (other than issuances of
refunding first mortgage bonds).  In addition, this restriction does
not prevent the creation or existence of:

    


    (a)           Liens
on property existing at the time of acquisition or construction of such property
(or created within one year after completion of such acquisition or
construction), whether by purchase, merger, construction or otherwise, or to
secure the payment of all or any part of the purchase price or construction cost
thereof, including the extension of any Liens to repairs, renewals,
replacements, substitutions, betterments, additions, extensions and improvements
then or thereafter made on the property subject thereto;

    


    (b)           Financing
of the Company’s accounts receivable for electric service;

    


    (c)           Any
extensions, renewals or replacements (or successive extensions, renewals or
replacements), in whole or in part, of liens permitted by the foregoing clauses;
and

    


    (d)           The
pledge of any bonds or other securities at any time issued under any of the
Secured Debt permitted by the above clauses.

    


    In
addition to the permitted issuances above, Secured Debt not otherwise so
permitted may be issued in an amount that does not exceed 15% of Net Tangible
Assets as defined below.

    


    “Net
Tangible Assets” means the total of all assets (including revaluations thereof
as a result of commercial appraisals, price level restatement or otherwise)
appearing on the Company’s balance sheet, net of applicable reserves and
deductions, but excluding goodwill, trade names, trademarks, patents,
unamortized debt discount and all other like intangible assets (which term shall
not be construed to include such revaluations), less the aggregate of the
Company’s current liabilities appearing on such balance sheet.  For
purposes of this definition, the Company’s balance sheet does not include assets
and liabilities of its subsidiaries.

    


    This
restriction also does not apply to or prevent the creation or existence of
leases made, or existing on property acquired, in the ordinary course of
business.

    


    SECTION
205.                                Place of
Payment

    


    The Place of Payment in respect of the
6.15% Senior Notes will be at the principal office or place of business of the
Trustee or its successor in trust under the Indenture, which, at the date
hereof, is located at 101 Barclay Street, New York, NY 10281, Attention:
Corporate Trust Department.

    


    SECTION
206.                                Sinking
Funds.

    


    Article
Twelve of the Indenture shall not apply to the 6.15% Senior Notes.

     

    SECTION
207.                                Redemption

    


    The 6.15% Senior Notes shall be
redeemable at the option of the Company, in whole at any time or in part from
time to time, upon not less than thirty but not more than sixty days’ previous
notice given by mail to the registered owners of the 6.15% Senior Notes at a
redemption price equal to the greater of (i) 100% of the principal amount of the
6.15% Senior Notes being redeemed and (ii) the sum of the present values of the
remaining scheduled payments of principal and interest on the 6.15% Senior Notes
being redeemed (excluding the portion of any such interest accrued to the date
of redemption) discounted (for purposes of determining present value) to the
redemption date on a semi-annual basis (assuming a 360-day year consisting of
twelve 30-day months) at the Treasury Rate (as defined below) plus 20 basis
points, plus, in each case, accrued interest thereon to the date of
redemption.

    


    “Comparable
Treasury Issue” means the United States Treasury security selected by an
Independent Investment Banker as having a maturity comparable to the remaining
term of the 6.15% Senior Notes that would be utilized, at the time of selection
and in accordance with customary financial practice, in pricing new issues of
corporate debt securities of comparable maturity to the remaining term of the
6.15% Senior Notes.

    


    “Comparable
Treasury Price” means, with respect to any redemption date, (1) the average of
the Reference Treasury Dealer Quotations for such redemption date after
excluding the highest and lowest such Reference Treasury Dealer Quotations, or
(2) if fewer than four such Reference Treasury Dealer Quotations are obtained,
the average of all such quotations.

    


    “Independent
Investment Banker” means one of the Reference Treasury Dealers appointed by the
Company and reasonably acceptable to the Trustee.

    


    “Reference
Treasury Dealer” means a primary U.S. government securities dealer in New York
City selected by the Company and reasonably acceptable to the
Trustee.

    


    “Reference
Treasury Dealer Quotation” means, with respect to each Reference Treasury Dealer
and any redemption date, the average, as determined by the Trustee, of the bid
and asked prices for the Comparable Treasury Issue (expressed in each case as a
percentage of its principal amount) quoted in writing to the Trustee by such
Reference Treasury Dealer at or before 5:00 p.m., New York City time, on the
third Business Day preceding such redemption date.

    


    “Treasury
Rate” means, with respect to any redemption date, the rate per annum equal to
the semi-annual equivalent yield to maturity of the Comparable Treasury Issue,
assuming a price for the Comparable Treasury Issue (expressed as a percentage of
its principal amount) equal to the Comparable Treasury Price for such redemption
date.

     

    ARTICLE
THREE

    Miscellaneous

    


    SECTION
301.                                Execution as Supplemental
Indenture

    


    This Sixth Supplemental Indenture is
executed and shall be construed as an indenture supplemental to the Original
Indenture and, as provided in the Original Indenture, this Sixth Supplemental
Indenture forms a part thereof.

    


    SECTION
302.                                Conflict with Trust
Indenture Act

    


    If any provision hereof limits,
qualifies or conflicts with another provision hereof which is required to be
included in this Sixth Supplemental Indenture by any of the provisions of the
Trust Indenture Act, such required provision shall control.

    


    SECTION
303.                                Effect of
Headings

    


    The Article and Section headings herein
are for convenience only and shall not affect the construction
hereof.

    


    SECTION
304.                                Successors and
Assigns

    


    All covenants and agreements by the
Company in this Sixth Supplemental Indenture shall bind its successors and
assigns, whether so expressed or not.

    


    SECTION
305.                                Separability
Clause

    


    In case any provision in this Sixth
Supplemental Indenture or in the 6.15% Senior Notes shall be invalid, illegal or
unenforceable, the validity, legality and enforceability of the remaining
provisions shall not in any way be affected or impaired thereby.

    


    SECTION
306.                                Benefits of Sixth
Supplemental Indenture

    


    Nothing in this Sixth Supplemental
Indenture or in the 6.15% Senior Notes, express or implied, shall give to any
Person, other than the parties hereto and their successors hereunder and the
Holders, any benefit or any legal or equitable right, remedy or claim under this
Sixth Supplemental Indenture.

    


    SECTION
307.                                Execution and
Counterparts

    


    This Sixth Supplemental Indenture may
be executed in any number of counterparts, each of which shall be deemed to be
an original, but all such counterparts shall together constitute but one and the
same instrument.

    


    
      
        
        

      

      
        
        

        
          

        

      

      
        
        

      

    

    IN WITNESS WHEREOF, the parties hereto
have caused this Sixth Supplemental Indenture to be duly executed and attested,
all as of the day and year first above written.

    


    


    PUBLIC SERVICE COMPANY OF
OKLAHOMA

    


    


    By:__/s/ Stephan T.
Haynes_________

    Stephan T. Haynes

    Assistant Treasurer

    


    


    Attest:

    


    


    __/s/ Jeffrey D.
Cross                                                                           

    Jeffrey D. Cross

    Assistant Secretary

    


    


    


    


    


    THE BANK OF NEW YORK,

    as Trustee

    


    


    By__/s/  Beata
Hryniewicka                                                                           

    Authorized Signatory

    


    


    


    Attest:

    


    


    _/s/ Van
Brown                                                                

    Name:  Van
Brown

    Title:    Vice
President

    


    


    
      
        
        

      

      
        
        

        
          

        

      

      
        
        

      

    

    


    STATE OF
OHIO                  
)

    : ss.:

    COUNTY OF
FRANKLIN    )

    


    


    On the 10th day of August, 2006,
personally appeared before me, a Notary Public within and for said County in the
State of Ohio, Stephan T. Haynes and Jeffrey D. Cross, to me known and known to
me to be respectively an Assistant Treasurer and an Assistant Secretary of
Public Service Company of Oklahoma, one of the corporations named in and which
executed the foregoing instrument, who severally acknowledged that they did sign
said instrument as such Assistant Treasurer and Assistant Secretary for and on
behalf of said corporation and that the same is their free act and deed as such
Assistant Treasurer and Assistant Secretary, respectively, and the free and
corporate act and deed of said corporation.

    


    In witness whereof, I have hereunto set
my hand notarial seal this 10th day of August, 2006.

    


    


    ___/s/ Leslye R.
Creek                                                                

    Notary Public, State of
Ohio

    Commission Expires
03-17-09

     

    
      
        
        

      

      
        
        

        
          

        

      

      
        
        

      

    

     

    STATE OF
NEW YORK       )

    : ss.:

    COUNTY OF
NEW YORK  )

    


    


    On the 10th day of
August, 2006, personally appeared before me, a Notary Public within and for said
County in the State of New York, Beata Hryniewicka and
Van Brown, to me known and known to me to be respectively the Assistant Vice
President and Vice President of The Bank of New York, one of the corporations
named in and which executed the foregoing instrument, who severally acknowledged
that they did sign said instrument as such Assistant Vice President and Vice
President for and on behalf of said corporation and that the same is their free
act and deed as such Assistant Vice President and Vice President, respectively,
and the free and corporate act and deed of said corporation.

    


    In witness whereof, I have hereunto set
my hand notarial seal this 10th day of
August, 2006.

    


    


    /s/ Carlos R.
Lociano                                                                           

    Carlos R. Lociano

    Notary Public, State of New
York

    Commission Expires
04-30-10

    


    


    


    
      
         

      

      
         

        
          

        

      

      
         

      

    

     

    
      Exhibit
A

       

      THIS
SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER
REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A NOMINEE OF A
DEPOSITARY.  THIS SECURITY IS EXCHANGEABLE FOR SECURITIES REGISTERED
IN THE NAME OF A PERSON OTHER THAN THE DEPOSITARY OR ITS NOMINEE ONLY IN THE
LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE, AND NO TRANSFER OF THIS
SECURITY (OTHER THAN A TRANSFER OF THIS SECURITY AS A WHOLE BY THE DEPOSITARY TO
A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY
OR ANOTHER NOMINEE OF THE DEPOSITARY) MAY BE REGISTERED EXCEPT IN LIMITED
CIRCUMSTANCES.

      


      Unless
this certificate is presented by an authorized representative of The Depository
Trust Company, a New York corporation (“DTC”), to Public Service Company of
Oklahoma or its agent for registration of transfer, exchange or payment, and any
definitive certificate issued is registered in the name of Cede & Co. or in
such other name as is requested by an authorized representative of DTC (and any
payment is made to Cede & Co. or to such other entity as is requested by an
authorized representative of DTC), ANY TRANSFER, PLEDGE, OR OTHER USE HEREOF FOR
VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL in as much as the registered
owner hereof, Cede & Co., has an interest herein.

      


      No.
R-1

      


      PUBLIC
SERVICE COMPANY OF OKLAHOMA

      6.15%
Senior Notes, Series F, due 2016

      


      CUSIP No.
744533 BH
2                                                                                                                                  $150,000,000

      


      PUBLIC
SERVICE COMPANY OF OKLAHOMA, a corporation duly organized and existing under the
laws of the State of Oklahoma (the “Company”, which term includes any successor
Person under the Indenture hereinafter referred to), for value received, hereby
promises to pay to CEDE & CO. or registered assigns, the principal sum of
ONE HUNDRED FIFTY MILLION DOLLARS ($150,000,000) on August 1, 2016 (the “Final
Maturity”), and to pay interest thereon from August 10, 2006 or from the most
recent Interest Payment Date to which interest has been paid or duly provided
for, semi-annually on February 1 and August 1 each year, commencing February 1,
2007, at the interest rate per annum specified above, until the principal amount
shall have been paid or duly provided for.  Interest shall be computed
on the basis of a 360-day year of twelve 30-day months.

      


      The
interest so payable, and punctually paid or duly provided for, on any Interest
Payment Date will, as provided in such Indenture, be paid to the Person in whose
name this Security (or one or more Predecessor Securities) is registered at the
close of business on the Regular Record Date for such interest, which shall be
the January 15 or July 15 (whether or not a Business Day) immediately preceding
the Interest Payment Date.  Any such interest not so punctually paid
or duly provided for will forthwith cease to be payable to the Holder on such
Regular Record Date and may either be paid to the Person in whose name this
Security (or one or more Predecessor Securities) is registered at the close of
business on a Special Record Date for the payment of such Defaulted Interest to
be fixed by the Trustee, notice whereof shall be given to Holders of Securities
of this series not less than 10 days prior to such Special Record Date, or be
paid at any time in any other lawful manner not inconsistent with the
requirements of any securities exchange on which the Securities of this series
may be listed, and upon such notice as may be required by such exchange, all as
more fully provided in said Indenture.

      


      Payment
of the principal of (and premium, if any) and interest on this Security will be
made at the office or agency of the Company maintained for that purpose in the
Borough of Manhattan, The City of New York, New York, in such coin or currency
of the United States of America as at the time of payment is legal tender for
the payment of public and private debts; provided, however, that at the option
of the Company payment of interest may be made by check mailed to the address of
the Person entitled thereto as such address shall appear in the Security
Register.

      


      This
Security has initially been issued in the form of a Global Security, and the
Company has initially designated The Depository Trust Company (the “Depositary”,
which term shall include any successor depositary) as the depositary for this
Security.  For as long as this Security or any portion hereof is
issued in such form, and notwithstanding the previous paragraph, all payments of
interest, principal and other amounts in respect of this Security or portion
thereof shall be made to the Depositary or its nominee in accordance with the
Applicable Procedures in the coin or currency specified above and as further
provided herein.

      


      This
Security is one of a duly authorized issue of securities of the Company (the
“Securities”), issued and to be issued in one or more series under an Indenture,
dated as of November 1, 2000, as amended and supplemented from time to time (the
“Indenture”, which term shall have the meaning assigned to it in such
instrument), between the Company and The Bank of New York, a New York banking
corporation, as Trustee (the “Trustee”, which term includes any successor
trustee under the Indenture), as to which Indenture and all indentures
supplemental thereto reference is hereby made for a statement of the respective
rights, limitations of rights, duties and immunities thereunder of the Company,
the Trustee and the Holders and of the terms upon which the Securities are, and
are to be, authenticated and delivered.  This Security is one of the
series designated on the face hereof, limited in aggregate principal amount to
$150,000,000; provided, however, the aggregate principal amount hereof can be
increased, without the consent of the Holder, as permitted by the provisions of
the Original Indenture.  The provisions of this Security, together
with the provisions of the Indenture, shall govern the rights, obligations,
duties and immunities of the Holder, the Company and the Trustee with respect to
this Security, provided that, if any provision of this Security necessarily
conflicts with any provision of the Indenture, the provision of this Security
shall be controlling to the fullest extent permitted under the
Indenture.

      


      The
Securities of this Series are subject to redemption upon not less than 30 nor
more than 60 days’ notice by mail to the Holders of such Securities at their
addresses in the Security Register for such Series at the option of the Company,
in whole or in part, from time to time at a Redemption Price equal to the
greater of (i) 100% of the principal amount of the Securities being redeemed and
(ii) the sum of the present values of the remaining scheduled payments of
principal and interest on the Securities being redeemed (excluding the portion
of any such interest accrued to the date of redemption) discounted (for purposes
of determining present value) to the redemption date on a semi-annual basis
(assuming a 360-day year consisting of twelve 30-day months) at the Treasury
Rate (as defined below) plus 20 basis points, plus, in each case, accrued
interest thereon to the date of redemption.

      


      “Comparable
Treasury Issue” means the United States Treasury security selected by an
Independent Investment Banker as having a maturity comparable to the remaining
term of the Securities that would be utilized, at the time of selection and in
accordance with customary financial practice, in pricing new issues of corporate
debt securities of comparable maturity to the remaining term of the
Securities.

      


      “Comparable
Treasury Price” means, with respect to any redemption date, (1) the average of
the Reference Treasury Dealer Quotations for such redemption date after
excluding the highest and lowest such Reference Treasury Dealer Quotations, or
(2) if fewer than four such Reference Treasury Dealer Quotations are obtained,
the average of all such quotations.

      


      “Independent
Investment Banker” means one of the Reference Treasury Dealers appointed by the
Company and reasonably acceptable to the Trustee.

      


      “Reference
Treasury Dealer” means a primary U. S. government securities dealer in New York
City selected by the Company and reasonably acceptable to the
Trustee.

      


      “Reference
Treasury Dealer Quotations” mean, with respect to each Reference Treasury Dealer
and any redemption date, the average, as determined by the Trustee, of the bid
and asked prices for the Comparable Treasury Issue (expressed in each case as a
percentage of its principal amount) quoted in writing to the Trustee by such
Reference Treasury Dealer at or before 5:00 p.m., New York City time, on the
third Business Day preceding such redemption date.

      


      “Treasury
Rate” means, with respect to any redemption date, the rate per annum equal to
the semi-annual equivalent yield to maturity of the Comparable Treasury Issue,
assuming a price for the Comparable Treasury Issue (expressed as a percentage of
its principal amount) equal to the Comparable Treasury Price for such redemption
date.

      


      If notice
has been given as provided in the Indenture and funds for redemption of any
Securities (or any portion thereof) called for redemption shall have been made
available on the Redemption Date referred to in such notice, such Securities (or
any portion thereof) will cease to bear interest on the date fixed for such
redemption specified in such notice and the only right of the Holders of such
Securities will be to receive payment of the Redemption Price.

      


      In the
event of redemption of this Security in part only, a new Security or Securities
of this Series and of like tenor for the unredeemed portion hereof will be
issued in the name of the Holder hereof upon the cancellation
hereof.

      


      The
Securities of this series will not be subject to any sinking fund.

      


      If an
Event of Default with respect to Securities of this series shall occur and be
continuing, the principal of the Securities of this series may be declared due
and payable in the manner and with the effect provided in the
Indenture.

      


      Interest
payments with respect to this Security will be computed and paid on the basis of
a 360-day year of twelve 30-day months for the actual number of days
elapsed.

      


      The
Indenture permits, with certain exceptions as therein provided, the amendment
thereof and the modification of the rights and obligations of the Company and
the rights of the Holders of the Securities of each series to be affected under
the Indenture at any time by the Company and the Trustee with the consent of the
Holders of a majority in principal amount of the Securities at the time
Outstanding of all series to be affected (voting as a class).  The
Indenture also contains provisions permitting the Holders of specified
percentages in principal amount of the Securities of each Series at the time
Outstanding, on behalf of the Holders of all Securities of such series, to waive
compliance by the Company with certain provisions of the Indenture and certain
past defaults under the Indenture and their consequences.  Any such
consent or waiver by the Holder of this Security shall be conclusive and binding
upon such Holder and upon all future Holders of this Security and of any
Security issued upon the registration of transfer hereof or in exchange herefor
or in lieu hereof, whether or not notation of such consent or waiver is made
upon this Security.

      


      No
reference herein to the Indenture and no provision of this Security or of the
Indenture shall alter or impair the obligation of the Company, which is absolute
and unconditional, to pay the principal of, premium, if any, and interest on
this Security at the times, place and rate, and in the coin or currency, herein
prescribed.

      


      This
Security shall be exchangeable for Securities registered in the names of Persons
other than the Depositary with respect to such series or its nominee only as
provided in the Indenture.  This Security shall be so exchangeable if
(x) the Depositary notifies the Company that it is unwilling or unable to
continue as Depositary for such series or at any time ceases to be a clearing
agency registered as such under the Exchange Act, (y) the Company executes and
delivers to the Trustee an Officers’ Certificate providing that this Security
shall be so exchangeable or (z) there shall have occurred and be continuing an
Event of Default with respect to the Securities of such
series.  Securities so issued in exchange for this Security shall be
of the same series, having the same interest rate, if any, and maturity and
having the same terms as this Security, in authorized denominations and in the
aggregate having the same principal amount as this Security and registered in
such names as the Depositary for such Global Security shall direct.

      


      As
provided in the Indenture and subject to certain limitations therein set forth,
the transfer of a Security of the series of which this Security is a part is
registrable in the Security Register, upon surrender of this Security for
registration of transfer at the office or agency of the Company in any place
where the principal of and any premium and interest on this Security are
payable, duly endorsed by, or accompanied by a written instrument of transfer in
form satisfactory to the Company and the Security Registrar duly executed by,
the Holder hereof or his attorney duly authorized in writing, and thereupon one
or more new Securities of this Series and of like tenor, of authorized
denominations and for the same aggregate principal amount, will be issued to the
designated transferee or transferees.

      


      The
Securities of this Series are issuable only in registered form without coupons
in denominations of $1,000 and any integral multiple thereof.  As
provided in the Indenture and subject to certain limitations therein set forth,
Securities of this Series are exchangeable for a like aggregate principal amount
of Securities of this Series and of like tenor of a different authorized
denomination, as requested by the Holder surrendering the same.

      


      No
service charge shall be made for any such registration of transfer or exchange,
but the Company may require payment of a sum sufficient to cover any tax or
other governmental charge payable in connection therewith.

      


      Prior to
due presentment of this Security for registration of transfer, the Company, the
Trustee and any agent of the Company or the Trustee may treat the Person in
whose name this Security is registered as the owner hereof for all purposes,
whether or not this Security be overdue, and neither the Company, the Trustee
nor any such agent shall be affected by notice to the contrary.

      


      For so
long as this Security is issued in the form of a Global Security, any notice to
be given to the Holder of this Security shall be deemed to have been duly given
to such Holder when given to the Depositary, or its nominee, in accordance with
its Applicable Procedures.  Neither the Company nor the Trustee will
have any responsibility with respect to those policies and procedures or for any
notices or other communications among the Depositary, its direct and indirect
participants and the beneficial owners of this Security in global
form.

      


      If at any
time this Security is not represented by a Global Security, any notice to be
given to the Holder of this Security shall be deemed to have been duly given to
such Holder upon the mailing of such notice to the Holder at such Holder’s
address as it appears on the Security Register maintained by the Company or its
agent as of the close of business preceding the day such notice is
given.

      


      Neither
the failure to give any notice nor any defect in any notice given to the Holder
of this Security or any other Security of this series will affect the
sufficiency of any notice given to another Holder of any Securities of this
series.

       

      The
Indenture provides that the Company, at its option, (a) will be discharged from
any and all obligations in respect of the Securities (except for certain
obligations to register the transfer or exchange of Securities, replace stolen,
lost or mutilated Securities, maintain paying agencies and hold moneys for
payment in trust) or (b) need not comply with certain restrictive covenants of
the Indenture, in each case if the Company deposits, in trust, with the Trustee
money or U.S. Government Obligations which, through the payment of interest
thereon and principal thereof in accordance with their terms, will provide
money, in an amount sufficient to pay all the principal of, and premium, if any,
and interest, if any, on the Securities on the dates such payments are due in
accordance with the terms of such Securities, and certain other conditions are
satisfied.

      


      No
recourse shall be had for the payment of the principal of or the interest on
this Security, or for any claim based hereon, or otherwise in respect hereof, or
based on or in respect of the Indenture or any indenture supplemental thereto,
against any incorporator, organizer, member, limited partner, stockholder,
officer or director, as such, past, present or future, of the Company or any
successor Person, whether by virtue of any constitution, statute or rule of law,
or by the enforcement of any assessment or penalty or otherwise, all such
liability being, by the acceptance hereof and as part of the consideration for
the issuance hereof, expressly waived and released.

      


      This
Security shall be governed by and construed in accordance with the laws of the
State of New York without regard to principles of conflict of law except Section
5-1401 of the New York General Obligations Law.

      


      All terms
used in this Security which are defined in the Indenture shall have the meanings
ascribed to them in the Indenture.

      


      Unless
the certificate of authentication hereon has been executed by the Trustee
referred to herein by manual signature, this Security shall not be entitled to
any benefit under the Indenture or be valid or obligatory for any
purpose.

      


      
        
           

        

        
           

          
            

          

        

        
           

        

      

      IN
WITNESS WHEREOF, Public Service Company of Oklahoma has caused this instrument
to be duly executed.

      


      
        	 
      	
                PUBLIC
      SERVICE COMPANY OF OKLAHOMA

              
	 
      	 
      	 
      
	 
      	
                By:

              	
                /s/
      Stephan T. Haynes

              
	 
      	 
      	
                Assistant
      Treasurer

              


      

      


      


      


      This is
one of the Securities of the series designated herein and referred to in the
within-mentioned Indenture.

      


      
        	
                Dated:  August
      10, 2006

              	
                THE
      BANK OF NEW YORK

              
	 
      	 
      	 
      
	 
      	
                By:

              	
                /s/
      Beata Hryniewicka

              
	 
      	 
      	
                Authorized
      Signatory

              


      

      


      


      
        
           

        

        
           

          
            

          

        

        
           

        

      

      


      FOR VALUE
RECEIVED, the undersigned hereby sell(s), assign(s) and transfer(s)
unto

      


      (PLEASE
INSERT SOCIAL SECURITY OR OTHER

         IDENTIFYING
NUMBER OF ASSIGNEE)

      


      _______________________________________

      


      ________________________________________________________________

      


      ________________________________________________________________

      (PLEASE
PRINT OR TYPE NAME AND ADDRESS, INCLUDING ZIP CODE, OF

      ________________________________________________________________

      ASSIGNEE)
the within Note and all rights thereunder, hereby

      ________________________________________________________________

      irrevocably
constituting and appointing such person attorney to

      ________________________________________________________________

      transfer
such Note on the books of the Issuer, with full

      ________________________________________________________________

      power of
substitution in the premises.

      


      


      


      Dated:________________________                                                                                     _________________________

      


      


      


      NOTICE:                      The
signature to this assignment must correspond with the name as written upon the
face of the within Note in every particular, without alteration or enlargement
or any change whatever and NOTICE:  Signature(s) must be guaranteed by
a financial institution that is a member of the Securities Transfer Agents
Medallion Program (“STAMP”), the Stock Exchange Medallion Program (“SEMP”) or
the New York Stock Exchange, Inc. Medallion Signature Program
(“MSP”).