These signs mean FREE Wi-Fi SPOT.
On our way back home, we stopped by at Joetsumyoko Station, a railway station located in Joetsu, Niigata Prefecture. At the station we didn't do anything particular: just looked around. There were some small shops and a cafeteria to get some rest in. If the weather had been good, we could have got a view of Mt. Myoko.
I only found this Wi-Fi sign...but a Wi-Fi sign for the first time in ages!