reater channel capacity-Each of the multiple channels offers substantial capacity. The capacity depends on where you are in the world. In the North American system, each channel in the cable TV system is 6MHz wide, according to the National Television Systems Committee (NTSC) standard. In Europe, with the Phase Alternate Line (PAL) standard, the channels are 8MHz wide. Within one of these channels, you can provision high-speed Chapter 2 Traditional Transmission Media Internet access-that's how cable modems operate. But that one channel is now being shared by everyone using that coax from that neighborhood node, which can range from 200 to 2,000 homes. Greater bandwidth-Compared to twisted-pair, coax provides greater bandwidth systemwide, and it also offers greater bandwidth for each chan- nel. Because it has greater bandwidth per channel, it supports a mixed range of services. Voice, data, and even video and multimedia can benefit from the enhanced capacity. Lower error rates-Because the inner conductor is in a Faraday shield, noise immunity is improved, and coax has lower error rates and therefore slightly better performance than twisted-pair. The error rate is generally 10-9 (i.e., 1 in 1 billion) bps. Greater spacing between amplifiers-Coax's cable shielding reduces noise and crosstalk, which means amplifiers can be spaced farther apart than with twisted-pair. The main disadvantages of coax are as follows: Problems with the deployment architecture-The bus topology in which coax is deployed is susceptible to congestion, noise, and security risks. Bidirectional upgrade required-In countries that have a history of cable TV, the cable systems were designed for broadcasting, not for interactive communications. Before they can offer to the subscriber any form of two- way services, those networks have to be upgraded to bidirectional systems. Great noise-The return path has some noise problems, and the end equip- ment requires added intelligence to take care of error control. High installation costs-Installation costs