This is a High current driver that will take the 5V TTL signal from your Arduino, etc and drive any all of the 4 relays. Three other channels are left open for other applications. It includes status LEDs for each input.
We offer multiple ways to convert RS232. We have 3-5V TTL converter cables, RS232 to USB, Ethernet converters, and USB to TTL converters. TTL converters allow you to communicate directly with your micro-controller or other TTL device. The RS232 to Ethernet devices allow you to bring serial RS232 equipment onto an Ethernet LAN/WAN.