I have 4 cameras in my system. Recently I installed a siren which i can manually turn on (switch). It is 12V. What hardware do I need to connect to my computer that I can connect the wires to the siren to and have Blue Iris trigger this siren when a camera is triggered.
I just recently wanted to do the same so I started testing with various devices and was finally able to come up with a simple & relatively cheap solution. I made a simple "How to" video on YouTube.