The signal isolator is used to provide galvanic isolation from one signal (input) to another (output) and usually combines the converter function. The isolator input, output and power supply are electrically isolated from each other making these units ideal for solving signal incompatibility and earth loop problems during process control system commissioning. This communication and broadcasting equipment come in three versions such as input signal powered, output loop powered and externally powered. Input signal powered isolators are used as a quick fix to unexpected isolation problems or as signal splitters to create extra isolated signal channels. They require no separate power supply as there is minimal effect on the wiring resulting in the lowest installed cost. Output loop powered signal isolators are often used to provide isolation for the analogue inputs into PLC or other receiving devices. Externally powered isolators can be used in all applications, because they incorporate their own power supplies, drive capability are higher than a two-wire transmitter.