For making remote 1 0 1 protocol adaptable to compatible application requirement of different transmission modes of modern electric automatic equipments,this paper states development history of IEC 60870-5-101 protocol,characteristics on link layer of unbalanced and balanced transmission modes of 1 0 1 protocol and necessity of transmission design for bal-anced mode of 1 0 1 protocol.Meanwhile,aiming at blank space in application of balanced transmission mode,it proposes se-lection mode design scheme for a kind of intelligent transmission mode and simulates field operational environment to pro...