Product specifications

COMMUNICATIONS
Sharp Electronics Corporation
When Noise Appears:
Noise is a fact of life. It is electromagnetic radiation and can come from many
sources including fluorescent lighting, motors, car ignition systems, equipment such
as hospital analyzers, transmission equipment from CB’s, truck, taxis, radio and
television broadcasters, and natural sources such as the sun.
When noise appears, and hits the two wires in our twisted pairs (Figure 6), the
electromagnetic radiation of the noise induces a voltage in both wires. However, the
direction is the same or "common mode" in both wires.
Figure 6
When the two noise signals reach either end of the cable, there is either a passive
balancing device (such as a transformer shown in Figure 6) or the equivalent active
balanced input. As you can see, the two noise signals on the two wires cancel each
other out. In this way, the noise cancels out and the signal (which is "differential
mode") can continue through.
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