|Object Name||Calculator, Pocket|
|Title||Texas Instruments SR-51A Calculator|
.01 The top has maker's name, number pad, compute keys, and sinh, cosh, tanh, RAN#, CONST, A%, log, 10x, var, mean, S. dev, X/, CM, exc, prod, E-, CD, EE, Fix PT buttons. The back has a removable panel for access to battery pack; the panel has a warning and operating instructions in raised letters on it.
.02 A black plastic case with the TI logo stamped on it and zipper closure (which doesn't work). The lining is of black material.
|Collection||Marshall W. Nirenberg Collection|
|Caption||Texas Instruments SR-51A Calculator|
Used by Dr. Marshall Nirenberg. This model of caculator was introduced in June 1975 for $224.95. The "A" in the model number means that it was identical to the SR-51 model except it had no inner rigid keyboard frame, LED display, or bubble-lens magnifier. So although it was a high-end calculator because of the number of functions and its accuracy to 13 digits, it was cheaper to make.
The almost simultaneous invention of integrated circuits ICs) by Jack Kilby of Texas instruments and Robert Noyce of Fairchild Instruments made led to major advances in electronics. This device in essence replaced the transistors, capacitors and resistors of conventional electronic circuits by miniature versions of these components. Integrated circuits are built by depositing alternate layers of semiconducting, conducting, resisting and insulating materials on a chip of germanium or more commonly silicon. Careful choice of those materials produced spots that emulate conventional electrical components. Arithmetical calculators comprised one of the early application of ICs, still today one of the main application of these devices. Though considerably more compact than their predecessors, IC-based calculators are restricted to the same four operations arithmetical operations: addition, subtraction, multiplication and division. The more complicated circuits made possible by advances in building ICs led to calculators that could handle more complex mathematics. The Hewlett Packard HPl 35 launched in 1972 is generally recognized as the first portable scientific calculators. Texas Instruments, home of the invention of ICs, launched their reply to the HP 35 in early 1975. As this calculator, the SR 50, was expensive to produce it was soon replaced by the SR 51 which incorporated some cost-saving modifications. The LC display in the SR 51 for example was replaced by a smaller CD bar behind a magnifier bubble. The SR 51A was promoted as a scientific-financial calculator in recognition of the higher mathematical capability. The SR 51A for example was capable of performing both trigonometric and statistical operations. The keyboard contained the 20 keys for performing arithmetic. An additional 15 keys are devoted to higher mathematical functions. The calculator was also equipped with a random number generator. The SR 51A was introduced in June 1975 at $224.95, by 1976. The SR51A like its counterpart the HP 35 has been credited with ending the long dominance for technical calculations of the slide rule.
|Number of images||3|
|Credit line||Dr. Alessandra Rovescalli, NHLBI|
|Organizations||NIH; NHLBI, Genetics and Developmental Biology|
|Buildings||Building 10 ("CC" Warren Grant Magnuson Clinical Center)|
|Serial #||SR-51A 138595|
Nirenberg, Marshall W.
Rovescalli, Alessandra C.