Galaxy
Access Control Panel
The 635 Series Access Control Panel, a dual serial interface, is engineered to improve third party integration, enhancing user convenience and ensuring interoperability with current and legacy hardware. The 635 DSI board includes two 485 ports to support 485 devices in a single or multi-drop configuration. The new board also allows more power connections and enhancements to be added to legacy systems. The system is available in four sizes and a rack mount version and can be populated with any combination of controller boards, including the new 635 DSI.
http://www.galaxysys.com/pdf/support/manuals/sghardware/600hardwaremanual.pdf