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DATAMATH CALCULATOR MUSEUM

Texas Instruments SR-40

Date of introduction:	June 13, 1976	Display technology:	LED-stick
New price:	$49.95, £26.95	Display size:	8 (5 + 2)
Size:	5.8" x 3.2" x 1.4"
Weight:	6.2 ounces	Serial No:	2200153
Batteries:	BP5, BP8	Date of manufacture:	wk 50 year 1976
AC-Adapter:	AC9131, AC9132	Origin of manufacture:	USA
Precision:	10	Integrated circuits:	TMC0981
Memories:	1
Program steps:		Courtesy of:	Joerg Woerner

The SR-40 was introduced mid of 1976 together with the entry calculator TI-30 and the financial calculator Business Analyst. These 3 calculators defined a new manufacturing approach within Texas Instruments. Everything is snapped together, no screws within the whole calculator. Compared with the SR-50A, SR-16-II and the failed SR-40 prototype the preceeding scientific calculators the electronics was squeezed dramatically. The elder calculators used a main printed circuit board (PCB) and a small daughter board carrying the display.

The SR-40 and all other (except the SR-51-II and TI-45) calculators in the Majestic-line used a LED-stick carrying the whole electronics! If you open such a calculator you'll find the LED-stick, one resistor and one integrated circuit in a 28 pin housing. That's all. If you are interested in the calculating accuracy of scientific calculators don't miss the Calculator forensics.

If we discover the sources of the components used in this SR-40 we locate:

	The LED chips were furnished by the SC Group in Dallas.
	The lens by an Ohio supplier.
	The circuit board and the IC are from TI Singapore.
	The board assembly was by TI Taiwan.
	The keyboard was made at TI Lubbock
	and assembled to the board in the Lubbock or Abilene plant.

Within the Majestic-line you'll find two base architectures with only small differences:

The entry line uses a 9-digit LED-stick giving either 8 digits display in normal mode or 5+2 digits in scientific mode. The calculators uses ON/OFF keys.

Simply by comparing the designation of the integrated circuits of the entry line "Majestic" calculators, you'll get the all members of this family:

	TMC0980 Goulds Pumpulator uses a custom design ROM (CD9801)
	TMC0981 TI-30 and SR-40
	TMC0982 Business Analyst and TI-41
	TMC0983 Programmer
	TMC0984 TI-33

Digging deeper into the TMC098x calculator chips you'll locate an OEM-chip used on a TI-30 "clone" manufactured in Hong Kong:

TMC0985 Amelia Scientific 2001

The upper line uses a 12-digit LED-stick giving either 8 or 10 digits in normal mode and 8+2 digits in scientific mode. The calculators use an ON/OFF slider.

The usage of these modern calculators was easy, Texas Instruments invented with the SR-52 the AOS entry that allowed up to three pending operations within the parantheses.

Later in production the metallized TI logo was replaced with an unmetallized. View here the SR-40 w/o chrome.

AOS™ is a trademark of Texas Instruments.

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