The 8 channel Opto Isolator board provides protection for my Raspberry Pi GPIO inputs, has a wide input Voltage range (5 to 24 Volt), and can interface to 3.3 Volt or 5 Volt signals depending on the Controller's requirements. Designed by Noop Labs, the pcb is very good quality with all components clearly identified. It is fully assembled, fully functional, and works like a charm. It is very versatile providing isolation protection while making interfacing to higher Voltage signals quick and easy. The documentation provided is concise but more than adequate for successful application. It also provides LEDs for visual indication of signal levels aiding in development and troubleshooting. Well worth the cost in time savings and piece of mind.