The TI 2500 "Datamath" was Texas Instruments first calculator, launched in early summer 1972. It was very successful and several versions were produced over the next few years. This is the TI-2500B "Datamath". Power supply use of either 3 NiCd batteries (3*1.2V=3.6V) or 4 alkaline batteries (4*1.5V=6.0V)