2PCS version. Provide online user manual, please check the manual carefully before using! ^^ Support USB to RS485 bidirectional conversion. Fast communication, stable and reliable, better compatibility ^^ Onboard TVS (Transient Voltage Suppressor), effectively suppress surge voltage and transient spike voltage in the circuit, lightningproof & anti-electrostatic ^^ Onboard resettable fuse and protection diodes, ensures the current/voltage stable outputs, provides over-current/over-voltage proof, improves shock resistance ^^ 3 LEDs for indicating the power and transceiver status