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                                                                    Exhibit 10.9


                  FOURTH AMENDMENT, dated as of February 26, 1999 (this "Fourth
Amendment"), to the Credit Agreement, dated as of August 29, 1996, as amended by
the First Amendment thereto dated as of January 29, 1997, the Second Amendment
thereto dated as of March 21, 1997 and the Third Amendment thereto dated as of
March 3, 1998 (the "Credit Agreement"), among WESTINGHOUSE ELECTRIC CORPORATION,
now known as CBS CORPORATION ("CBS"), the Subsidiary Borrowers parties thereto,
the Lenders parties thereto, NATIONSBANK, N.A. and THE TORONTO-DOMINION BANK, as
Syndication Agents, THE CHASE MANHATTAN BANK, as Documentation Agent, and MORGAN
GUARANTY TRUST COMPANY OF NEW YORK, as Administrative Agent. Unless otherwise
specified herein, all capitalized terms defined in the Credit Agreement and used
herein are so used as so defined.


                              W I T N E S S E T H :
                              ---------------------

                  WHEREAS, CBS wishes to amend the Credit Agreement in the
manner set forth herein; and

                  WHEREAS, each of the parties hereto is willing to enter into
this Fourth Amendment on the terms and subject to the conditions set forth
herein;

                  NOW, THEREFORE, in consideration of the premises and for other
good and valuable consideration the receipt and sufficiency of which is hereby
acknowledged, the parties hereto hereby agree as follows:


                  ARTICLE I--AMENDMENTS TO THE CREDIT AGREEMENT

                  1. Section 1.1. (a) The definition of "Consolidated EBITDA"
contained in Section 1.1 of the Credit Agreement is hereby amended and restated
in its entirety as follows:

                  "Consolidated EBITDA" shall mean, with respect to CBS and its
         Consolidated Subsidiaries for any period, operating profit (loss)
         (excluding that related to Discontinued Operations), plus other income
         (loss), plus interest income, plus depreciation and amortization
         (excluding amortization related to programming rights), excluding (a)
         gains (losses) on sales of assets (except (I) gains (losses) on sales
         of inventory sold in the ordinary course of business and (II) gains
         (losses) on sales of other assets if such gains (losses) are less than
         $10,000,000 individually and less than $50,000,000 in the aggregate
         during such period), and (b) other non-cash items (including (i)
         provisions for losses and additions to valuation allowances, (ii)
         provisions for restructuring, litigation and environmental reserves and
         losses on the Disposition of businesses and (iii) pension settlement
         charges), in each case determined for such period on a basis consistent
         with that reported in CBS's Form 10-Q for the fiscal quarter ended
         September 30, 1998 filed with the SEC, minus cash payments made during
         such period in respect of non-cash charges taken during any previous
         period (excluding cash payments in respect of non-cash charges taken
         prior to December 31, 1998).

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                  (b) The date "December 31, 1998" set forth in the definition
of "Consolidated Total Funded Indebtedness" is hereby changed to the date "June
30, 1999".

                  2. Section 1.2(c). Section 1.2(c) of the Credit Agreement is
hereby amended by adding the following new clause (iv) to the end thereof:

         "; and (iv) the financial results and effects of the operations of the
         Eye on People and TeleNoticias businesses shall be entirely
         disregarded"

                  3. Section 5.6(a). Clause (v) of Section 5.6(a) of the Credit
Agreement is hereby amended and restated in its entirety as follows:

         "(v) Indebtedness incurred on any date when, after giving effect
         thereto, the aggregate principal amount of Indebtedness incurred
         pursuant to this clause (v) that is outstanding on such date (it being
         understood that, for the purposes of this clause (v), the term
         "Indebtedness" does not include borrowings under this Agreement or
         Excluded Indebtedness) does not exceed the greater of (x) $750,000,000
         and (y) consolidated EBITDA of Infinity and its consolidated
         Subsidiaries (determined in a manner comparable to that set forth in
         the definition of "Consolidated EBITDA") for the most recent period of
         four consecutive fiscal quarters for which the relevant financial
         information is available less, in the case of any such Indebtedness
         incurred by Infinity or any of its consolidated Subsidiaries, the then
         actual aggregate outstanding balances of Indebtedness incurred pursuant
         to this clause (v) by Subsidiaries other than Infinity and its
         consolidated Subsidiaries, provided that the aggregate outstanding
         principal amount of Indebtedness incurred pursuant to this clause (v)
         by Subsidiaries other than Infinity and its consolidated Subsidiaries
         shall not exceed $300,000,000 at any time"

                  4. Article VI. Paragraph (d) of Article VI is hereby amended
by adding the following parenthetical to the end of subclause (ii)(x) thereof:

         "(provided that this subclause (ii)(x) shall not apply to any provision
         that permits the holders, or a trustee on their behalf, to cause
         Indebtedness to become due prior to its stated maturity because of the
         failure to deliver to such holders or such trustee financial statements
         or certificates for any Subsidiary that is not required by law or
         regulation to file financial statements with the SEC, unless such
         Indebtedness has become due prior to its stated maturity as a result of
         such failure)"

                  5. Commitment Reduction. Effective on the Fourth Amendment
Effective Date (as defined below), the aggregate Commitments shall be
permanently reduced from $4,000,000,000 to $3,000,000,000.


                            ARTICLE II--MISCELLANEOUS

                  1 Representations and Warranties. CBS and each Subsidiary
Borrower (to the extent specifically applicable to such Subsidiary Borrower)
hereby represents and warrants, on and as of the Fourth Amendment Effective Date
(as defined below), that (a) the execution and delivery of this Fourth Amendment
and the performance of this Fourth Amendment and the Credit Agreement as amended
by this Fourth Amendment (the "Amended Credit Agreement") will not conflict with
or result in a breach of, or require any consent under, the charter or By-laws
(or other equivalent organizational documents) of CBS or any Subsidiary
Borrower, or any applicable law or regulation, 


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or any order, writ, injunction or decree of any Governmental Authority, or any
material agreement or instrument to which CBS or any of its Material
Subsidiaries is a party or by which any of them is bound or to which any of them
is subject, or constitute a default under any such agreement or instrument, or
result in the creation or imposition of any Lien upon any of the revenues or
assets of CBS or any of its Material Subsidiaries pursuant to the terms of any
such agreement or instrument; (b) CBS and each Subsidiary Borrower has all
necessary corporate power and authority to execute and deliver this Fourth
Amendment and to perform its obligations under this Fourth Amendment and the
Amended Credit Agreement; (c) the execution and delivery of this Fourth
Amendment and the performance of this Fourth Amendment and the Amended Credit
Agreement have been duly authorized by all necessary corporate action on the
part of CBS and each Subsidiary Borrower; (d) this Fourth Amendment has been
duly and validly executed and delivered by CBS and each Subsidiary Borrower and
each of this Fourth Amendment and the Amended Credit Agreement constitutes a
legal, valid and binding obligation of CBS and each Subsidiary Borrower,
enforceable in accordance with its terms except as such enforceability may be
limited by (i) bankruptcy, insolvency, reorganization, moratorium, fraudulent
transfer or similar laws of general applicability affecting the enforcement of
creditors' rights and (ii) the application of general principles of equity
(regardless of whether such enforceability is considered in a proceeding in
equity or at law); (e) no authorizations, approvals or consents of, and no
filings or registrations with, any Governmental Authority are necessary for the
execution and delivery by CBS and each Subsidiary Borrower of this Fourth
Amendment, for the performance by CBS and each Subsidiary Borrower of this
Fourth Amendment and the Amended Credit Agreement or for the validity or
enforceability hereof or thereof; and (f) each of the representations of CBS and
each Subsidiary Borrower set forth in Article III of the Amended Credit
Agreement is true and correct in all material respects on and as of the Fourth
Amendment Effective Date with the same effect as though made on and as of such
date, except to the extent such representations and warranties expressly relate
to an earlier date in which case such representations and warranties were true
and correct in all material respects as of such earlier date.

                  2 No Other Modifications. Except as expressly modified hereby,
all the provisions of the Credit Agreement are and shall continue to be in full
force and effect. Each reference in the Credit Agreement to "this Agreement",
"hereunder", "hereof" and words of like import referring to the Credit Agreement
shall mean the Credit Agreement as amended hereby.

                  3 GOVERNING LAW. THIS FOURTH AMENDMENT SHALL BE CONSTRUED IN
ACCORDANCE WITH AND GOVERNED BY THE LAWS OF THE STATE OF NEW YORK APPLICABLE TO
AGREEMENTS MADE WITHIN SUCH STATE, WITHOUT REGARD TO CONFLICTS OF LAW PROVISIONS
AND PRINCIPLES OF SUCH STATE.

                  4 Counterparts. This Fourth Amendment may be executed by one
or more of the parties to this Fourth Amendment on any number of separate
counterparts, and all of said counterparts taken together shall be deemed to
constitute one and the same instrument.

                  5 Effectiveness. This Fourth Amendment shall become effective
on the date (the "Fourth Amendment Effective Date") upon which the
Administrative Agent shall have received (a) an executed counterpart of this
Fourth Amendment from CBS and each Subsidiary Borrower and (b) executed Lender
Consent Letters (or facsimile transmissions thereof) from the Required Lenders
consenting to the execution of this Fourth Amendment by the Administrative
Agent, provided that, subject to receipt of the foregoing items, the amendments
described in Sections 1, 2, 3 and 4 of Article I of this Fourth Amendment shall
be deemed to be effective as of December 31, 1998.


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                  IN WITNESS WHEREOF, the parties hereto have caused this Fourth
Amendment to be duly executed by their respective authorized officers as of the
day and year first above written.


                                   CBS CORPORATION

                                   By     /s/ Fredric G. Reynolds             
                                     -------------------------------------------
                                   Title:


                                   INFINITY BROADCASTING CORPORATION

                                   By     /s/ Farid Suleman                   
                                     -------------------------------------------
                                   Title:


                                   HEMISPHERE BROADCASTING CORPORATION

                                   By     /s/ Fredric G. Reynolds             
                                     -------------------------------------------
                                   Title:


                                   INFINITY BROADCASTING CORPORATION OF BOSTON

                                   By     /s/ Fredric G. Reynolds             
                                     -------------------------------------------
                                   Title:


                                   INFINITY BROADCASTING CORPORATION OF NEW YORK

                                   By     /s/ Fredric G. Reynolds             
                                     -------------------------------------------
                                   Title:


                                   TRANSPORTATION DISPLAYS, INCORPORATED

                                   By     /s/ Farid Suleman                   
                                     -------------------------------------------
                                   Title:


                                   MORGAN GUARANTY TRUST COMPANY OF NEW YORK,
                                   as Administrative Agent

                                   By     /s/ Robert Bottamedi                
                                     -------------------------------------------
                                   Title: Vice President