For 10/100Mbps connectivity, three basic options are available for different PHY. The first option is a six core circuit which includes one common mode choke, one isolation transformer, and one autotransformer per twisted pair. The second option is a four core circuit. This includes one three-wire common mode choke and one isolation transformer per pair. The third option is another four core circuit that includes one two-wire common mode choke and one isolation transformer per pair. Although each option allows data transmission at 10/100Mbps, each option will perform differently in regards to EMI.