USB serial port control relay, upgraded and advanced version, featuring a optocoupler protection circuit to prevent interference and support speed serial transmission. Key benefits Optocoupler isolation reduces interference from load circuits and enables fast, reliable serial control. USB serial port control provides simple integration with PCs and microcontroller projects. Built in overcurrent protection enhances safety and protects both the module and connected devices. The output terminals function as an electronic switch with no voltage output on the load end from the module itself; external supply is required for the load. What it does When there is no voltage in the relay coil, the common terminal (COM) is connected to the normally closed terminal (NC). When the coil is energized, the relay pulls in and COM connects to the normally open terminal (NO). The module's output terminals serve as a switching element to enable or disable the connected circuit. Important characteristics Function: USB serial port controlled relay with optocoupler protection and overcurrent protection. Control: USB serial interface for direct control of the relay coil. Protection: Optocoupler protection circuit to prevent interference and support speed transmission. Safety: Overcurrent protection for the module and connected loads. Output behavior: The module does not supply voltage to the load end; it acts as an electronic switch for an external power source. 23 practical use scenarios Home automation: Use the USB serial interface to switch lighting, fans, or other devices by controlling the relay coil, with isolation to minimize noise affecting the control computer or microcontroller. Smallscale industrial control: Integrate with a USBenabled controller to activate sensors, indicators, or actuators, benefiting from isolation and protection features in a compact form factor. Laboratory and DIY projects: Interface with microcontrollers or PCs to control external circuits, test relays, or sequence experiments without risking interference or damage to the control device. Notes The load side of the module is a switched connection; provide the appropriate external supply to power the load. Clean, reliable switching is achieved through the optocoupler protection circuit and the reinforced control path over USB serial control.