tomers. The agreement specifies that in four years, customers of Verizon and the cable TV operators will be able to receive a single bill for mobile, TV, broadband, and voice services. Prior to that, the partners will sell the services to one another's customers, but MSOs and Verizon will continue to bill for services on their networks. Profit margins will be lower than sales of services on their own networks, but capital and operating expenses will be minimized on the wholesale offerings. In December 2011, Cox also entered into an agreement to sell spectrum to Veri- zon. The agreed upon price was $315 million. They further decided to sell each other's services and to collaborate on ways to integrate wireless and wireline services. Cox is selling only a portion of its spectrum to Verizon. Other Competitors to Broadband Providers Overbuilders were the first facilities-based competitors to cable TV operators. They began offering service immediately following passage of the Telecommunications Act of 1996, which permits competitors to offer services "over" incumbent cable TV oper- ator's equipment. Overbuilders run their cables over incumbent MSOs' cables on tele- phone poles in residential neighborhoods. However, they reuse the drop wires installed by the incumbent cable TV operator. A drop wire is the cable from the telephone pole to an individual residence. RCN and Atlantic Broadband are examples of overbuilders. In contrast to direct broadcast satellite television, overbuilders offer voice tele- phone service and Internet access in addition to pay-TV. Some also sell services to business customers in areas where they operate. The State of the Industry However, overbuilders underestimated the cost of building and maintaining these networks. They also overestimated their ability to win customers from incumbent cable television operators. One factor in the difficulty of attracting enough customers to be profitable was their lack of financial heft to mount the widespread TV and print advertising campaigns incumbents m