Royal DT 80 (Version 1)

Date of introduction:  1984 Display technology:  LCD
New price:   Display size:  8
Size:  4.7" x 4.1" x 1.0"
 120 x 106 x 25 mm3
Weight:  3.0 ounces, 86 grams Serial No:  
Batteries:  n.a.  Date of manufacture:  mth 10 year 1984
AC-Adapter:   Origin of manufacture:  Taiwan
Precision:  8  Integrated circuits:  Sharp LI3135MS
Memories:  1    
Program steps:   Courtesy of:  Joerg Woerner

Does this Royal DT 80 calculator sold in 1984 look familiar to you?

Dismantling the featured DT 80 manufactured in October 1984 by Cal-Comp Electronics, an OEM (Original Equipment Manufacturer) in Taiwan, reveals a clean design centered around a Sharp LI3135MS single-chip calculator circuit soldered on a double-sided printed circuit board (PCB) and powered by solar cells.

Inspecting the PCB of this DT 80 brought our attention to a small mark reading SD9-12, most likely a reference to Type Small Desktop 9 and Revision 1.2 of the design (schematics and layout). We spotted similar PCB-Mark already with the near identical offspring TI-1795 and Radio Shack EC-2006A with revisions SD9-13, SD9-14, and SD-9-15. We started compiling a list of the PCB-Marks on calculators manufactured by OEMs for Texas Instruments.

The DT 80 was soon replaced replaced with a 2nd Version sporting smaller solar cells.

If you have additions to the above article please email:

Joerg Woerner, August 2, 2023. No reprints without written permission.