4N37VM by onsemi is a transistor output optocouplers designed for reliable performance in electronic applications. It is widely used in industrial, automotive, and power management systems.

Isolator products are used where it is necessary to pass information, control signals, or gate drive signals between portions of a system that must not have a direct electrical connection with each other, whether for functional or safety-related reasons. Within this category, devices are further organized according to the character of their output stages; some device outputs behave like transistor, others like logic gates, photovoltaic (solar) cells, thyristors, or photoresistors.