Anyone know what the third hole in airline headphone jacks are for? It's smaller than the other two in use. : r/whatisthisthing
Dual 3.5mm Male to 3.5mm Female Airplane Headphone Adapter Gold Plated (2 Pack)
InLine® Audio Plane headphone adpter cable, 2x 3.5mm M to 3.5mm F 3pin, 0.15m | Y-Adapter Cable | Jack -> jack | Cable | Product Overview | INTOS ELECTRONIC AG - Online Store