Extending USB to 4CH RS485 allows concurrent and independent communication for each channelOnboard TVS (Transient Voltage Suppressor) effectively suppress surge voltage and transient spike voltage in the circuit lightningproof & anti-electrostaticOnboard resettable fuse and protection diodes ensures the current/voltage stable outputs provides over-current/over-voltage proof improves shock proof performanceOnboard RS485 output terminal 120R resistors enabled/disabled via DIP switchAluminium alloy case with oxidation dull-polish surface CNC process opening solid and durable well-crafted