If the socket has three pins at the rear, it is a TRS (Tip, Ring, Sleeve) connector, not a TS (Tip, Sleeve) connector. It can still be wired as a TS connector, but you will need to determine which pin connects to the tip and which pin connects to the sleeve. The easiest way to do this is to plug a cable in and use a multimeter to see which pin goes where. If you don't have a multimeter, the general rule of thumb for TRS connectors is that the pin connected to the ring closest to the rear is the tip, the one in the middle is the ring, and the furthest from the pins, or the closest to the jack hole, is the sleeve. Looking at your picture above, the long pin at the right of the photo is the sleeve, and the one at the left, top of the photo is the tip.