From PTI Security Systems
The RS-485 converter changes serial RS-485 data to serial RS-232 data. It is used on Digigitech DigiGraphics and PTI Site Graphics devices so that the PCs that display the graphics can communicate to their respective controllers over the RS-485 data line.
The converter requires a separate power source, which is a plug in wall transformer. Output of this transformer should be 12VDC @ 200ma.