ATEN RS232&lt;-&gt;RS422/RS485 Reversible Converter with Multidrop & Isolated Surge Protection IC485AI (Black) Automatic internal RS-485 bus supervision No external flow control signals for RS-485 required Transient suppression on RS-485 data lines Data transimission controlled by the RTS signal Unit Dimensions 2.9 x 0.7 x 2.1; Unit Pack Wt. 0.95 lb.