s for Businesses A Comparison of T1 and E1 T1 technology is used only in North America and Japan. The rest of the world uses E1, which operates at 2.048Mbps on 32 channels-30 channels for voice or data, one channel for signaling, and one channel for framing (assigning bits to channels and maintaining synchronization with external clock sources) and remote maintenance. T1/E1 and T3/E3 depend on strict adherence to timing. Each individual channel is referred to as a digital signal zero (DS-0). A DS-0 runs at 56Kbps or 64Kbps on T1 and E1 circuits. The DS-0 speed of 64Kbps is the same worldwide. (See Table 5-2 in the "Appendix" section at the end of this chapter for vari- ous digital signal levels.) Organizations that link a T1 or E1 in the United States to an office in Europe need rate adaptation equipment SO that the carrier in the United States can connect the domestic T1 to the European E1 line. Rate adaption equipment converts E1 signals to those compatible with T1, and vice versa. Carriers supply rate adaptation equipment in their networks. A Comparison of T3, J3, and E3 Worldwide Standards DS-3 speeds differ internationally. The T3 North American speed is 44Mbps over 672 channels (28 X 24 = 672)-the equivalent of 28 T1s. The Japanese "flavor," J3, operates at 32Mbps over 480 channels. This is the equivalent of 20 T1s. The E3 speed is 34Mbps over 480 channels. E3 is the equivalent of 16 E1s. T3 services are also offered at fractional speeds. For example, fractional T3 is offered at speeds of 10Mbps. However, customers who want fractional T3 often opt for the lower-speed Carrier Gigabit Ethernet, where it's available. This provides a more scalable solution and is not limited to 44Mbps. T1/E1, T3/E3, the Internet, and Public Switched Telephone Network Access T1/E1 and T3/E3 services are used mainly for network access. Access to the Public Switched Telephone Network (PSTN) for an organization's voice traffic is a com- mon application for TDM. Quality is guaranteed because a time slot is saved for each Broadband a