However, its expense limits application. Each repeater in the series adds a small amount of jitter to every pulse of the bit stream. A conservative limit of 200 tandem repeaters in a system ensures that the accumulated jitter won't exceed the synchronization capability of terminal equipment or higher-order multiplexers. Design Criteria Long-range design of the span line is necessary to plan the expected cross section of the span. The number of systems that can be installed in a single cable is mainly controlled by the physical separation of the pairs in the two directions of transmission.
Greater separation increases the coupling loss, resulting in decreased interference.
A general rule is that if transmit and receive pairs are in the same cable binder group, the maximum section loss should be reduced to 15 dB to prevent crosstalk. In two-cable operation, NEXT does not limit the number of systems for one cable.