Built in 2KV surge protector. Built in 15KV Electrostatic Discharge. 9 24V AC/DC. ADDC (Automatic Data Direction Control). RS-422 data control. Auto Baud Rate Sensing- Switch setting for RS-422. Over current protection when 2 signals are shortened together at the RS-422 / 485 end. 32 Units connected together in RS-485 multi-drive operation. Built-in termination resistors.