meslots are placed in the 125-microsecond frame, resulting in a payload of 240 bits per frame, a payload rate of 1.920 Mbs, and a total channel rate of 2.048 Mbs. Another major difference and significant improvement of E1 over T1 structure is increased overhead. From the start, this was a troubling characteristic of T1, not because it was too much, but because it wasn't enough. There was never a standard method, nor enough bits to deal with the many overhead requirements for voice service. Besides, when data transport came on the scene, US DSO channels could reliably deal with only 56 Kbs instead of the entire 64 Kbs bandwidth. So the designers of E1 digital facilities added 2 to 64 Kbs channels providing 128 Kbs. Adding these two timeslots in the 125-microsecond frame resulted in 256 bits in each frame, 240 for payload and 16 for overhead. PRACTICAL IP AND TELECOM FOR BROADCAST ENGINEERING AND OPERATIONS CHANNEL RATE VS. MULTIPLEX RATE One of the major points of confusion, both inside and outside the Telecom industry is the misunderstanding and misuse of channel interface and multiplex rate terms. In publication after publication, the PDH hierarchy is explained by simply calling out the various multiplex levels or signal rates without delineating the difference between the rates that specify channel rates through the network, and the rates resulting from multiplexing. Channel rates apply to channel interface, which is the point of network access and egress. Table 4-1 shows most of the PDH multiplex aggre- gate rates and channel rates covered by global and national standards. Basically, the standards are structured toward use in three regions: Europe and the rest of world (E), except North America (T) and Japan (J). Multiplex levels generally are designated with a DS, meaning digi- tal signal (level) and channel interface and bandwidth with a T, E, or J. Another factor that is often completely missed is the fact that telecom networks are dominated by voice traffic. The nature of voice traffic caused the network t