The SDM-SIO1 has lower power biasing of its inputs and no internal termination resistors, so it operates in the lowest power state. However, this means it can quite easily detect noise on the RS-422 cable, which can, for instance, be picked up from power leads. A simple solution to this is to add 120R termination resistors at one or both ends of the cable. Although termination resistors are only normally needed on long cable runs, they are also quite effective at reducing noise.