[Blindmath] Where can I get a Braille Slide Rule?

[Lloyd Rasmussen]

I have a braille slide rule here at my desk as a curiosity, but I'm not 
parting with it.

The American Foundation for the Blind used to produce talking books on 
phonograph records.  They had all the equipment for making the master, the 
mother, the stamper and the pressed discs in-house.  Until the early 1960s 
they were 12 inch discs.  Later they were 10-inch.

AFB created and sold all sorts of aids and appliances in the period up to 
the early 80s, and they used their record-pressing expertise to make 
braille slide rules.  The first model, which I have, was based on the 
12-inch format and is, to me, a superior product.  On one side it has dual 
pointers which can be locked together or decoupled.  This side has a 
logarithmic scale, so it is used for multiplication and division.  The 
other side of the record had a linear scale and a third pointer which was 
permanently locked to one on the front side.  The scale on the reverse side 
was linear, so you could determine base-10 logarithms of numbers by 
rotating the primary pointer to a number on the front side and then read 
the answer on the back.

The pointers came out almost to the circumference of the disc, where there 
were various combinations of single, double and triple dots to allow you to 
interpolate to better than  one percent accuracy.  Numbers for the scales 
were embossed an inch inside the circumference, so they were covered by the 
pointer.  But since there were only 9 or 10 of these numbers, you could 
figure out where you were by what was not covered by the large pointer.

This was one of my primary calculating tools, along with a Cranmer abacus 
and some braille math tables, in going through electronics engineering 
school from 1966-69 at Iowa State University.

The 10-inch version of the slide rule, necessitated by unavailability of a 
12-inch record press on premises, had poorer resolution, especially for 
determining logarithms, and probably disappeared from the market around 
1975-77 as talking calculators began to be produced.

I don't think you can find this equipment anymore except in a museum or 
perhaps on eBay.

At 08:01 AM 7/10/2009, you wrote:
>      Do you know where I can get a Braille Slide Rule?  I used to have a
>circular one.
>
>                Jerry
>

Lloyd Rasmussen, Senior Project Engineer, Engineering Section
National Library Service for the Blind and Physically Handicapped
Library of Congress    (202) 707-0535   <http://www.loc.gov/nls>
HOME:  <http://lras.home.sprynet.com>
The opinions expressed here are my own and do not necessarily represent 
those of NLS.