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.