Tallies and Contact Closures

Tallies and contact closures are simple open collectors (tallies) or relays (contact closures) that the switcher uses to signal other devices, and users, that a particular video source is on-air. Typically, tallies are used to light a red light on a camera to show people that they are on-air and what camera they should be looking at.

You can only assign a single source to a tally/contact closure, but you can assign multiple tallies/contact closures to the same source.