RS-232 to RS-422 / RS-485 Converter Card 

Features 
PCI/ISA Bus interface
Input: RS-232 protocol
Output: RS-485/422 protocol
"Self Tuner" inside
Speed: 300~115,200 bps 
256 modules max. in one RS-485 network without repeater
2048 modules max. in one RS-485 network with repeater
DC to DC isolation : 3000 Vdc
Repeater request: 4,000 feet or over 256 modules

Manual