The latency of the relay board is very small as it runs @ 19200 baud. I actually cleaned up the final version of script for this board and had one for testing. It was quite fast.

Note that if you want 2-way on this board, you should search this forum for posts by me containing the word UART as you should be aware that Serial ports 3 and 4 on RFX9600 use shared UART. There are implications such that you will want to either not use one of these ports (use 3 or 4 but not both is 2-2-way 232 is in use - risk losing data) or put 1-way devices on these ports and use Ports 1 and 2 for 2-way.