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DATAMATH CALCULATOR MUSEUM

Texas Instruments SR-50

Date of introduction:	January 15, 1974	Display technology:	LED modules + lens
New price:	$169.95, DM 520.00	Display size:	10 + 2
Size:	5.8" x 3.2" x 1.3"
Weight:	9 ounces	Serial No:	211917
Batteries:	BP1	Date of manufacture:	wk 42 year 1974
AC-Adapter:	AC9200	Origin of manufacture:	USA
Precision:	13	Integrated circuits:	TMC0501, TMC0521
Memories:	1
Program steps:		Courtesy of:	Joerg Woerner
		Download manual:	(US: 5.315 kB)

The wonderful electronic slide rule SR-50 marked a milestone in the history of calculators manufactured by Texas Instruments. It added trigonometric and hyperbolic functions, the logarithms and their inverses to the scientific functions of the SR-10, SR-11 and SR-16 line of calculators. The calculator was placed with big success against Hewlett-Packard's HP-35 and produced in high quantity. The internal construction was very rigid compared with other models. To reduce manufacturing costs and to give a similar appearence to the SR-52 and SR-56 calculators the SR-50 was replaced within 18 month with the SR-50A. Don't miss the rare SR-51.

On a first view the twins SR-50 and SR-50A look similar, but if you use them you'll feel the differences ! If you search for the best SR-50, choose a model produced later than July, 1974 ! Engineers at Texas Instruments changed the calculation algorithms and achieved a higher precision. Please find the comparision in the Calculator forensics.

With the TMC0501 building blocks Texas Instruments created a novel architecture for scalable scientific calculators. The architecture used minimum a 2 chip design with the Arithmetic chip and the SCOM (scanning read only memory) but was expandable to a maximum of 8 SCOM's, additional RAM as program memory for programmable calculators, additional RAM for general purpose registers and even a chip driving a printer. Most scientific and programmable calculators from Texas Instruments between the years 1974 and 1982 like the SR-51, SR-60A and TI-59 use these chips. Please find all known calculators using the TMC0501 architecture here. Don't miss the odd TI-5230 desktop calculator.

Masaki Takada donated some wonderful pictures and this gives us the opportunity to view the inside of the SR-50.

Engineers use the clear case during the development of a product to check if the electronic and mechanical components fit neatly into the housing.
The side view gives you an impression of the upper and lower case shell and the printed circuit boards inside.
The bottom view gives you (from upper right to lower left) the opening of the rechargable batteries, the huge calculator chips (TMC0501, TMC0521) and the power supply circuit.
The display frame covers the upper row of the keys and the two switches neatly. This gives you a very valuable design compared to e.g. the TI-30.
This wonderful pictures gives you an imagination of the curved lens above the red display. A perfect calculator!

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