HDSL has a longer range than T1 without the use of repeaters to allow transmission over distances up to 3.6km. The name has become more generic over time to refer to symmetric service at a variety of rates over a single loop. Cable modems are devices that attach to the cable TV network connection in a residence. There are a number of challenges faced by this industry including bi-directional data transfers as well as customer service issues and the lack of standards. However, potential bandwidth estimates range upwards of 30 Mbps from the service provider to subscriber.
Cable networks are inherently different in design than telephone networks.
Cable networks are broadcast oriented, with each subscriber in an area receiving the same signals - effectively a party line. There can be significant security and over-subscription issues as a result. A DSL circuit is dedicated to an individual user or company location, and is independent of all other DSL circuits. Cable networks, on the other hand, are inherently hierarchical in nature and thus require two paths, one for downstream and one for upstream. This requires either a second cable plant for upstream or a second frequency band allocated onto the existing system.