High-speed Internet access and residential telephony service are two good examples. Built on the existing video distribution network, these services offer new revenue streams that leverage the operator s existing network investment. Subscribers usually pay a monthly fee for the service, plus a fee for cable TV services. Each telephone jack is connected to the one twisted pair in the house telephone wiring, providing a new phone line for the house. The NIUs on the side of the house vary from vendor to vendor, providing one or multiple new phone lines.
Subscribers typically pay a monthly fee for each phone line activated.
Depending on the technology selected by the NIU vendor, different headend equipment and different network bandwidth are required to provide telephone service. Deploying circuit-switched Figure 1 shows a network architecture that provides telephony to cable subscribers. In this architecture, the operator chose to deploy an overlay telephony network at the service level for example, it uses the same coax cable to the home, but the operator has separated voice and data bandwidth over the cable. This is how cable telephony is provided today. Key telephony services, including caller ID, call waiting and three-way calling, are available.