On the 905 datasheet, what should the transformer turn ratio be? What value should I use for the termination resistors? The transmit twisted pair interface ratio should be 1:2 with 25ohm series termination resistors or a transformer ratio of 1:2 with 11.8 termination resistors. This makes the effective lineside impedance 100W. Revision 2.7 of the LXT905 datasheet has been updated to maintain consistency with a turn ratio of 1:2 with 11.8 resistors.