Broadcom, HCPL-4100-000E DC Input Transistor Output Optocoupler, Through Hole, 8-Pin DIP

Data line transmission, with high noise immunity between electronic equipment, is achieved by using these 20mA current loop transmitter and receiver optocouplers for typical distances up to 9km.

4mA-to-20mA Current-Loop Communication

Current loop systems are used in electrically noisy industrial environments for sending analogue sensor data over long distances of 300m or more.