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DATAMATH CALCULATOR MUSEUM

Texas Instruments SR-51 (early model)

Date of introduction:	January 1975	Display technology:	LED modules + lens
New price:	$224.95, DM 748.00	Display size:	10 + 2
Size:	5.8" x 3.2" x 1.3" 147 x 81 x 32 mm³
Weight:	8.5 ounces, 240 grams	Serial No:	10563
Batteries:	BP1	Date of manufacture:	wk 05 year 1975
AC-Adapter:	AC9200	Origin of manufacture:	USA
Precision:	13	Integrated circuits:	TMC0501, TMS0522, TMC0523
Memories:	3
Program steps:		Courtesy of:	Joerg Woerner

With the SR-51 Texas Instruments started a series of scientific calculators that added statistical functions and conversions to the "usual functions". You'll find similar performance and keyboard layout in the line SR-51 -> SR-51A -> SR-51-II -> TI-55 -> TI-55-II -> TI-55-III. But none of them was done as perfect as the SR-51. It was designed to stay decades as the close relative SR-50. Compared to the previous models the SR-51 got a keyboard design with white, grey, yellow and orange keys and gave an outlook to later TI calculators.

To reduce manufacturing costs and to give a similar appearence to the SR-52 and SR-56 calculators the SR-51 was replaced within few month with the SR-51A. Logically it's quite rare.

Nevertheless there are two different variants known:
This model from an early production lot with huge yellow characters for the shifted 2^nd-functions and later SR-51 with a finer printing.
(Kirk B. Muri provided the picture on the right. Thanks!)

The SR-51 was introduced in January, 1975 nevertheless the firmware of the calculator was released alreadt three month earlier. Pleas notice the Date code 7442 printed on the TMC0523 SCOM (scanning read only memory) chip storing part of the program of the calculator.

Interesting to know, this calculator works with the PC-100 "Printer Craddle" developed for the SR-52 and SR-56.

If you have additions to the above article please email: joerg@datamath.org.