What is the Trig port on my Tobii Pro TX300?

Tobii Pro TX300 Tobii Pro
The Trig port on the Tobii Pro TX300 is meant to receive 0-5V TTL signals using a 50 Ohms BNC cable from other devices (i.e. Cedrus Stimtracker).
The sync signal received from other devices will be retrieved in Tobii Pro Lab or Tobii Pro Studio.