As shown in the picture, when the output current exceeds 40mA the internal resistance 50? in the XTR110 (R9) should be replaced by external resistance REXT. REXT is connected between the 13 foot and 16 foot. REXY=R9(original span/required span). For example, the XTR110 in the picture`s original span is 20mA and now the required span is 10A. If R9=50?, then..