One time i was exploring an closed school / orphanage home(?) with some others. It had rooms for a lot of kids to live in. The old part was from the 1900s~ while extended around 1970~ and then got shut down. During this extension they added some sort of intercoms in each room to alarm guardians or something of this kind. While exploring during the day we found nothing at all to be wrong, nothing was on or running. That said, the school still had electric turned on but "abounded" or rather, not inn use for a long time.

While we explored the upper floors on the old part of the school, time went by and it got dark. At later - we decided to go back to the newer parts to explore again, and at this time we took notice that one of these intercoms was on and simply transmitting an empty signal of "white noise". Nothing else was heard. But whats kind of creepy is that none of us left each other side during this time and we didn't hear anything else before this.

Idk how it got turned on.