Ca(+)/H(+) antiporter that extrudes calcium in exchange for external protons. Does not transport sodium or potassium. Calcium efflux is tightly regulated by intracellular pH. Homotrimer. Transcriptionally regulated by the forespore-specific sigma factor, SigG, and the general stress response regulator, SigB. Belongs to the Ca(2+):cation antiporter (CaCA) (TC 2.A.19) family. Cation/proton exchanger (CAX) subfamily.