This excerpt taken from the CCO 8-K filed Dec 11, 2009.
Mandatory Redemption; Offers to Purchase; Open Market Purchases
We are not required to make any sinking fund payments with respect to the 2017 B Notes. Under certain circumstances, we may be required to offer to purchase 2017 B Notes as described under the caption Repurchase at the Option of Holders. We and our affiliates may at any time and from time to time purchase 2017 B Notes in the open market or otherwise. Notwithstanding the foregoing, none of the Company or any of its Subsidiaries shall make any purchase of, or otherwise effectively cancel or retire any 2017 B Notes (whether through open market purchases, tender offers, defeasance, offers to purchase required by the 2017 B Notes or otherwise) if, after giving effect thereto and, if applicable, any concurrent purchase of or other action with respect to any 2017 A Notes, the ratio of (a) the outstanding aggregate principal amount of the 2017 B Notes to (b) the outstanding aggregate principal amount of the 2017 A Notes shall be less than 0.250; provided, however, that the foregoing restriction shall not be applicable in the case of any Change of Control Offer, Asset Sale Offer or offer to purchase the 2017 A Notes required to be made under the 2017 A Indenture at the price specified with respect thereto to all holders of the 2017 A Notes, where a violation of the foregoing restriction would occur solely as a result of different offer acceptance rates by the holders of the 2017 B Notes and the 2017 A Notes. References to the 2017 B Notes and the 2017 A Notes in this paragraph do not include any Additional 2017 B Notes or any Additional 2017 A Notes, as applicable.