集成电路的数字数据传输--Integrated Circuits for Digital Data TransmissionIt is frequently necessary to transmit digital data in ahigh-noise environment where ordinary integrated logic circuitscannot be used because they do not have sufficientnoise immunity. One solution to this problem, of course, is touse high-noise-immunity logic. In many cases, this approachwould require worst case logic swings of 30V, requiring highpower-supply voltages. Further, considerable power wouldbe needed to transmit these voltage levels at high speed.This is especially true if the lines must be terminated to eliminatereflections, since practical transmission lines have alow characteristic impedance.A much better solution is to convert the ground referred digitaldata at the transmission end into a differential signal andtransmit this down a balanced, twisted-pair line. At the receivingend, any induced noise, or voltage due toground-loop currents, appears equally on both ends of thetwisted-pair line. Hence, a receiver which responds only tothe differential signal from the line will reject the undesiredsignals even with moderate voltage swings from the transmitter.