A: They are triggered by sound.
A: They are sound activated, as someone that reviewed the product said, "Takes a very loud noise to get these to come on"
A: This item has a timer feature which allows the item to stay on for 6 hours and automatically shut off for 18 hours. Hope this helps! Thanks! Mia, PAC Customer Service
A: No, this unit does not have sensors.
A: Hello Holly, they are sound activated. Put them in sensor mode, make a noise, and the stakes will light up and play their sound effect. You can also put them in timer mode where the lights will be on for 6 hrs a day (no sound plays in timer mode).
A: The full length is 86 inches. Your remaining question cannot be answered at this time.