Regular two-way IR diodes and sensors were standard on 90's business laptops for ordinary RS-232 file transfer between machines wirelessly. Before wifi or even

Regular two-way IR diodes and sensors were standard on 90's business laptops for ordinary RS-232 file transfer between machines wirelessly. Before wifi or even ethernet was everywhere, and before USB and Bluetooth came along. The first smartphones had it too so you could dial up the internet on the road in the years before phones had a browser and stuff like that.