anyone know?

i have these senders for my digital air gauges does anyone know what the prongs on the back mean? the one on left has a s. by it and the other has a w.l./g. what do these stand for?? help i have the pics up in my profile

i would think the s is for the sender and the other not sure

All the ones I installed one side was a ground, the other went to the gauge.

thanks guys one was a ground