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Monroe 820A Desktop Calculator

Front cover of Monroe 820A "Instruction" Pamphlet, Published in 1970

Image from July, 1970 Monroe Calculator Product Summary

14 pound, four-function office calculator. Fixed and automatic floating decimal settings. Two register, 14-digit CRT display, with seven-segment digit rendition. Small-scale DTL IC technology. Touted at time of introduction (August, 1969) as being the smallest CRT-display desktop calculator in the world. At the time, and to this day, this title holds true. By the late 1960's, CRT display technology was too expensive compared to gas-discharge and vacuum fluorescent display technology. With intense price competition in the market, bottom line manufacturing costs needed to be kept to a minimum, which made the CRT display a thing of the past. It appears that two versions of the machine were made -- initial production machines were the Monroe 820, however, shortly after sales began, likely in late 1969, a minor change was implemented that added an accumulation mode to the machine which created the 820A. The 820A has the accumulation mode switch located between the left-most group of keys and the numeric keypad, while on the 820, this area of the keyboard is blank. The modification did not involve any changes to the main logic of the machine. The modification was attached to the keyboard assembly, consisting of a small circuit board with a couple of IC's on it along with the switch. An added cutout was made on the keyboard bezel to accomodate the accumulation mode switch. The front panel of both machines reads MONROE 820, no change was made to this designation for the "A" model. 820A models were designated as such on the model/serial number tag located on the bottom of the cabinet. The museum is looking for any Monroe 820 or 820A calculators. If you have one, please contact us by clicking on the EMail button at the top of this page. Monroe 820 calculators were produced at Monroe's calculator plant in Lexington, South Carolina.