 a shared media to transmit data among them. Two main technologies are specifically designed to address this issue in backplanes of complex equipment. For each of these techniques, both input/output electronics chips and specific design rules are available. Single-ended or unbalanced communication is a technique characterized by the fact that one signal from a driver is carried on one wire or on one TDM frame slot to a receiver. The receiver compares the signal to a reference level with respect to ground. If differential or balanced communication is applied, both the signal and its complement are sent from the transmitted to the receiver. The driver sends this differential signal pair on two matched wires to a receiver, and the receiver compares the two signals with each other. This topology offers noise immunity advantages over most single-ended technologies. Because the two differential signals are compared to each other and not to a ground or logical local reference, noise or ground shifts that affect both inputs equally will be ignored by the receiver. Also, most differential technology signal swings are offset from both grounds furthering input noise immunity. Single-ended setups are much simpler than differential ones because they use half the signal lines, but noise can be a problem. For this reason, some systems benefit from dif- ferential signaling because of its superior noise immunity. Table 6.19 summarize the advantages and disadvantages of single-ended and differen- tial topologies. Last key point in backplane design is the choice of the temporization scheme among synchronous, source-synchronous, or asynchronous signal interfaces. Telecommunication Networks TABLE 6.19 Advantages and Disadvantages of Single-Ended and Differential Bus Topologies Single-Ended Advantages Disadvantages Less expensive Lower data transfer rates per bit Easy implementation Susceptibility to noise More compact, less real estate Many technologies available Higher drive capability available Differential Advantages Disadvantages