5.22 Texas Instruments Slide Rule Calculator

the beginning of the end…

TI SR-10 Calculator TI SR-50 Calculator
Model Year Serial Case Notes
SR-10 1974 SR10 892927 no gift of Brian Eddy (thanks!); version 2; original box
SR-50 1974 SR50 0224435 yes received for Christmas, high school, Sr. Year; leather case, instruction book

These Texas Instruments calculators were two of the models that one can say led to the end of slide rule use in the world. With Texas Instruments and Hewlett-Packard leading the way, hand-held calculators were suddenly becoming affordable to average professionals and serious students. The SR-10, first introduced in late 1972, sold for $149.95. Within a few months the price of version 2 of the SR-10 was $89.95. The SR-50, introduced in January 1974, has essentially all of the functionality of the scales we see on the slide rules of the collection – including hyperbolic functions. It computes factorials, which are not directly performed on slide rules, and displays numbers in scientific notation keeping track of the decimal point, as did the SR-10. Its initial retail price was $169.95. About 14 months later it was roughly $100. (See ISRM web site.)

With 10-digit or so accuracy in the results, slide rules were simply set to the side as we all gawked and played with our new friends. The average prices for these calculators kept coming down and reached into the $30 range in the next few years. Eventually the “SR” designation was removed from the new devices. In June of 1976 the TI-30 calculator, which replaced the SR-30, sold for only $24.95. These miracles of technology outperformed and cost less than the more expensive slide rules of the day. By the end of 1976 essentially all of the major manufacturers had stopped producing slide rules.

Below is an image of the calculators I have owned and used professionally. My first computer science course was in college in 1976 and I predominantly used computers, both main frame and personal, for most computations by 1985. From 1990 until 1998 or so these calculators one-by-one were relegated to the back of desk drawers next to my high school Sterling slide rules for the next 25+ years, as laptops and cell phone applications took over the role of performing desktop calculations.

Left-to-Right: Texas Instruments Calculators SR-50 (1974) , TI-37 (solar; 1985), TI-60 (1988), and TI-68 (1990). Note that only the SR-50 is designated as a “slide rule calculator”. Unfortunately my favorite – the TI-54 (1981) slanted LCD calculator with complex number functionality – was destroyed in a flooded office in 1988 and replaced by the TI-60 above.

Update! – For an incredibly low price I was able to obtain a replacement TI-54 in 2022. A fully functional New Old Stock item complete with instruction book, quick reference guide, and leather case in the original box.