What is an electrical socket with four holes in the shape of a square?

I just moved into a new condo in Chi, and adjacent to all of the electrical sockets is another receptacle that has four small holes in the shape of a square. In total it is about the same size as a normal electrical socket, but it is square and has holes the size of a headphone jack. It seems like it might be a foreign socket, or something that I don't even know. Any help would be greatly appreciated.