Signal isolators are single or dual linear current or voltage signal input single or dual current or voltage signal, transmitter output isolation and improve the performance of electrically isolated input, output, power supply. Uses signal during transmission will encounter a variety of interference in order to ensure signal stability, using signal isolation is particularly important. First, the working principle of the PLC signal received by the semiconductor device modulation conversion, and then converted by an optical isolation sense or magnetic induction device, and then transformed back to pre demodulate the original signal or isolate different signals, while the power supply signal is isolated after isolation, and to ensure the absolute independence between the converted signal, power, ground. Immunity measure interference power system design for sensors, instrumentation to work against the most serious is the interference power spikes. Peak interference generated electrical equipment are: welding, large motors, controlled machines, relay contacts, inflatable lights with ballasts, and so on. Peak interference available hardware, software, and (or) a combination of hardware and software approach to suppress.