Current Telco Services
Conventional wisdom is that phone wire is too restrictive for high-speed service because customers are accustomed to phone conversations and 56 Kbps modem service. However, the basic characteristics of phone w ire have the capacity to carry millions of bits per second. The reason they don't is that present voice service is provided in analog mode and filters are installed on phone interfaces and loops that suppress signals above 3400 Hz. Given these filters, the data-carrying capacity of phone wire is limited to 56 Kbps, using the latest generation of V.90 modems. Other services, operating in a digital mode, occupy bandwidth such as those shown in Table 4-1.