Impedance upper connected to main unit of existing wire communication system

A conventional wire communication system communicates between powered terminals via a main unit. In this system, the main unit communicates with the powered terminal by changing the voltage signal to the positive and the negative. The powered terminal communicates with the main unit using the reply current signal. Because this system is used for on-off control, the communication speed is slow. Then, we proposed the add-on type multiplex module to be able to do communications at speeds higher than conventional systems. The input impedance of the main unit is very low though the multiplex module communicates by increasing the input impedance. In this paper, we propose the impedance upper connected to the main unit for steady communications, and describe the basic characteristics.