Four independent PC817 optocoupler channels on a single board, enabling simultaneous control of multiple loads with electrical isolation between input and output sides. Jumper cap selectable output mode per channel to suit your circuit: level output or pulldown (lowlevel) output. This flexible configuration lets you adapt to different load drivers and logic requirements without changing circuitry. Onboard isolation improves safety and noise immunity by keeping control signals separate from the highervoltage or noisy load side, protecting microcontrollers and control electronics. Simple, compact design for easy integration into projects, prototypes, and small automation tasks. Clear separation of input and output connections simplifies wiring and troubleshooting. Each channel operates independently, so you can drive four loads with different control needs at the same time without crosschannel interference. Compatible with standard control signals on the input side and suitable for interfacing microcontrollers with highervoltage or noisy load circuits such as relays, transistors, or other switching devices. Practical use scenarios: 1) Microcontroller to relay/driver interface: use one or more channels to isolate control signals from relay coils or current drivers, protecting the MCU. 2) Sensor isolation in automation: connect sensors to the input side while keeping the processing electronics isolated from potential electrical noise or spikes on the sensor/Nload side. 3) Prototyping multichannel control: configure different channels with either level or pulldown outputs to test which configuration provides the interface for your load drivers, all on one board. Key attributes: function to provide galvanic isolation, independent fourchannel operation, jumpercap selectable output mode, simple wiring, and support for various control applications requiring reliable isolation.