RS-232 to RS-485 Converter

Features 
Input : RS-232 protocol
Output : RS-485 protocol (two wire, D+, D-)
Speed : auto switching baud rate, 300~115200 bps 
Internal "Self Tuner"  
Maximum of 256 modules. in a single RS-485 network without using a repeater 
Maximum of 2048 modules. in a single RS-485 network when using a  repeater
Isolation voltage: 3000Vdc on the RS-232 side 
Repeater request: 4,000 feet or over 256 modules

Manual