The second light is an indication that the Travelvision antenna is ready for searching for the satellite.
If you have placed the control module in the system and you switch the connected receiver / TV on any TV channel (not on standby mode), the 2nd green light on the power inserter will light up.
At that time, the control module also lights up and you can use the system to search for a satellite.
The 2nd light goes out again when the satellite is found and after it is fully optimized / focused on the satellite. Or if you removed the control module from the system.