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The Texas Instruments SR-51A, is an early scientific calculator produced by Texas Instruments, with production beginning in 1975.

Texas Instruments SR-51A
TI SR-51A.jpg
TypeScientific calculator
PredecessorTI SR-51
Cost225 USD
Entry modeAlgebraic
Display typeBubble LED
Power supplyAC adapter, internal proprietary battery, or aftermarket battery
Power consumption0.473 to 1.113W

Internal design[edit | edit source]

The SR-51A consists of two boards, one with the keypad matrix and another with the calculator logic, power supply circuitry, and display. Unlike many more modern calculators from Texas Instruments, metal domes are used for the keypad, giving it a crisp tactile feel, reminiscent of HP calculator keypads. The keypad matrix is connected to the main board by way of a wide ribbon cable, and the back side of the keypad board is well insulated to prevent short circuits on the main board.

All of the calculations are carried out on the TMC0501 calculator ASIC a pair of stacked ROM chips are included alongside it, the TMC0522 and TMC0523 which store the data pertaining to the scientific functions of the calculator.

Internal boards from a SR-51A

External resources[edit | edit source]

See also[edit | edit source]