ISDN (Integrated Services Digital Network) is a kind of phone service offered by most local telephone companies. It has many benefits, but most important is the ability to carry one voice and two high-speed data or video communications channels over existing copper wire in the home. This generally means there's no need to install new phone lines to give telecommuters the separate voice and data lines they often need. The cost of ISDN service is generally less than the equivalent number of separate lines. However, ISDN is not universally available in the US and other countries; thus, telecommuters and their employers can't always get access to it when needed. Also, there are one-time equipment costs for the special phones and for the devices needed to connect PCs to ISDN lines. On balance, it's a technology that should be considered but may not always be available, or cost-effective even if it is available.