datamath ti-2500

here is a rather splendid datamath calculator from texas instruments. the ti-2500 first released in 1972 had six different versions. this example is version 2 and dates from 1973.

the unit is powered by 4 AA cells inside the unit and is meant to be used in conjunction with the mains adapter which charges the batteries for up to 15 hours.

notice the peculiarity of placing the add and subtract buttons down the right and the multiply and divide across the top. at first, i expected the unit to operate like a desk calculator (eg 3+2- rather than 3-2-=), but it doesnt, it operates like any 4 function unit would today.

the power switch is on the left side of the machine and a switch on the klixon keyboard selects between chain or const operation. const is a way of activating multiply and divide constants like 2*3=, 4=, 5= in the normal way. a similar selector is available on the desktop ti-3500.