Features: With 8 channels of RS485 communication, the R413D08 module is the perfect solution for your Modbus-RTU protocol and AT command needs. Under the AT command ,the maximum delay is 9999 seconds；Under the MODBUS command ,themaximum delay is 255 seconds AT commands can be made serialHyperTerminal (serialassistant) Enter; MODBUS commands can be made serialHyperTerminal (serialassistant) OR ''Modbus Poll'' Enter; With RS485 and RS232TTL dualbus interface；8pcs Output controlpins, 5VTTL level, low level (default) / high level output Specifications: Item：RS485 Modbus DC: 5V / 6V 24V Optional Operating Current : 10-15MA Support：RTU protocol AT instruction Length:approx 45mm/1.77in for Relay Switch Board PLCControl Package Includes: 1PC RS485 Modbus note: Due to the problems of lighting effects and shooting angles, there will be certain tolerances in the product, please understand. Please allow 0-1cm error due to the manual measurment.