Blackmagic Design GPI and Tally Interface - SWTALGPI8

8 inputs / 8 outputs
Indicates "on-air" status
Contact Closure    
25 pin D-type connector providing 8 opto isolated inputs and 8 relay contact closure outputs
Inputs
Optical isolators triggered by connection to ground. Max 5V at 14mA.
Outputs
Mechanical relay contact closure to ground. Max 30V at 1A.
Ethernet
10/100 BaseT with loop through for connecting to other ethernet enabled equipment
Computer Interface
1 x USB 2.0 high speed interface for configuration and firmware updates

GPI and Tally Interface connects to an ATEM switcher and provides 8 contact closure Tally outputs. 

Tallies will be displayed when connected to an ATEM switcher to indicate their "on-air" status and you can even connect multiple interfaces together to increase the number of tally outputs.