A tally light is a small signal-lamp on a professional video camera or monitor. It is usually located above the lens or on the electronic viewfinder and communicates that the camera is 'live' - i.e. its signal is being used for the 'main program' at that moment.
Tally light systems by MetaSETZ (http://www.metasetz.com) are currently the only systems supported by Livestream Studio.
Once you have acquired your Tally Light system, connect it to your computer via an available USB port. The system should recognize it and automatically install the drivers.
Open the Livestream Studio™ software and open Settings > Advanced.
Under 'Other,' check the 'Tally Lights' option. Save your settings.
Go to the Input Settings tab and select the camera to which you want to assign a tally port.
Select 'Tally' and assign one of the available tally ports to your camera as seen below:
When the camera is set to Program, the selected Tally Light will turn on.