The Series 9164 mA isolating repeater allows two 4 to 20 mA signal sources to be coupled. For example, it allows 4-wire transmitters to be connected to I/O cards designed to be operated with two wires. The use of this device therefore saves costs by eliminating the need for additional I/O cards, or it can be used as the only solution for I/O cards that only operate with two wires.