* [[Differential amplifier]]s or receivers that respond only to voltage differences, ''e.g.,'' those between the wires that constitute a pair. This method is particularly suited for instrumentation where signals are transmitted through DC bias.
* An inductor where a pair of signalling wires follow the same path through the inductor. Eg in a [[bifilar winding]] configuration such as used in Ethernet magnetics.<ref>http://ww2.pulseeng.com/products/datasheets/H325.pdf</ref> Useful for AC and DC signals, but will filter only higher frequency common mode signals.
An* inductorA wheretransformer, awhich pairis ofuseful signallingfor wiresAC followsignals theonly, sameand pathwill throughfilter theany inductor.form Egof common mode noise, but may be used in combination with a [[bifilar winding]]wound configurationcoil suchto aseliminate usedcapacitive coupling of higher frequency common mode signals across the transformer. Used in Ethernettwisted magneticspair Ethernet.<ref>http://ww2.pulseeng.com/products/datasheets/H325.pdf</ref> Useful for AC and DC signals, but will filter only higher frequency common mode signals.
A transformer, which is useful for AC signals only, and will filter any form of common mode noise, but may be used in combination with a bifilar wound coil to eliminate capacitive coupling of higher frequency common mode signals across the transformer. Used in twisted pair Ethernet.<ref>http://ww2.pulseeng.com/products/datasheets/H325.pdf</ref>
Common mode filtering may also be used to prevent egress of noise for electromagnetic compatibility purposes;
