Texas Instruments

• datamath

Model: TI-2511
Battery: 4 x AA alkaline
Adapter: AC9900/e
Year: 1974
Chip: TMS0119
Info: 1 version

• basic

Model: TI-2550
Battery: 3*AA NiCd or 4*AA Alkaline 
Adapter: AC9130 or AC9120
Year: 1974
Chip: TMS0601
Info: Released one year after the legendary TI-2500, the first with a lens display (like bubbles)

• basic

Model: TI-2550 II
Battery: 2 AA or BP2
Adapter: 
Year: 1976
Chip: TMS1071
Info:

• basic

Model: TI-2550 III
Battery: BP3
Adapter: AC9130A
Year: 1976
Chip: TMS1043
Info:

• basic

Model: TI-2550 IV
Battery: BP4
Adapter: AC9900/H
Year: 1979
Chip: TMC1981,TMC0999
Info: