## Friday, March 24, 2017

### Retro Review: Garrett CM 20 Calculator

Retro Review:  Garrett CM 20 Calculator

Introduction

 Is it Pac Man or is it a calculator?

I bet if Pac Man and Ms. Pac Man ever used a calculator, it is this one: the Garrett CM 20 calculator.  I received this calculator as a present from my good friend Chris Brame in Illinois.  Many thanks and appreciation, and it is hit with the household.

There is close to no information for the Garrett CM 20, only to find that model originated in 1973, predating the famous Pac Man game by seven years.  On the bottom label, the Garrett Comtronics Corporation is located in San Diego, California.  The CM 20 was made in the United States.

The CM 20 is AC powered, with the power switch on the back of the calculator.

A Spherical Delight

The CM 20 comes has a spherical design.  Garrett also produced several calculators with a spherical design, the CM 25 and CM 35.  The CM 25 has memory functions.

The keyboard on the CM 20 is just a delight; the keys are light to the touch and easy on the fingers.  Also, the keys are responsive.

Check out the display, the digits are orange!

The A/B and % Keys

The CM 20 is a real basic four function calculator, without memory or a square root key.  However, the CM 20 has an A/B key, which works as a “Last X” key (think scientific keystroke programmable calculators from Hewlett Packard).  After a pending operation completes (+, -, *, or ÷), press the A/B key to recall the last number entered before completing the operation.  For example:

6 [ + ] 3 [ = ]   (Display:  9)  Pressing [A/B] recalls 3 (and puts 9 in the temporary register)

3 [ + ] 6 [ = ]   (Display:  9)  Pressing [A/B] recalls 6 (and puts 9 in the temporary register)

75 [ ÷ ] 15 [ = ]  (Display: 5)   Pressing [A/B] recalls 15.

And so on.

The percentage key works a little bit different from most four-function calculators.  On the CM 20, you are required to press the equals key to complete the operation.  To find out a percentage of a number, enter the base, press any of the arithmetic keys, the percentage and the % key.  To illustrate:

25 [ + ] 15 [ % ]  (Display: 3.75) [ = ] (Display 18.75 = 25 + 15%)

25 [ - ] 15 [ % ]  (Display: 3.75) [ = ] (Display 21.25 = 25 – 15%)

25 [ * ] 15 [ % ]  (Display: 3.75) [ = ] (Display 93.75 = 25 * 3.75 = 25 * (25 * 15%))

25 [ ÷  ] 15 [ % ]  (Display: 3.75) [ = ] (Display 166.66666 = 25 / 0.15)

25 [ + ]/[ - ]/[ * ]/[ ÷ ] 15 [ % ] Stop.  (Display:  3.75 = 25 * 15%)

Final Verdict

This calculator is going to be on my desk for a long time.  I love the retro 1970s design and the spherical shape of the calculator.  Thank you Chris!

Eddie

This blog is property of Edward Shore, 2017