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Datexx DB-403

Date of introduction:  2003 Display technology:  LCD
New price:  MSRP $22.00 (2020) Display size:  8
Size:  3.0" x 6.2" x 0.30"
 75 x 157 x 7 mm3
   
Weight:  2.2 ounces, 62 grams Serial No:  
Batteries:  LR54 Date of manufacture:  mth 12 year 2014
AC-Adapter:   Origin of manufacture:  China
Precision:  8  Integrated circuits:  unknown
Memories:  3    
Program steps:   Courtesy of:  Joerg Woerner
    Download manual:   (US: 0.8 MByte)

National Semiconductor introduced already in 1978 with the NS103 Data Checker an electronic record keeper with three continuous memories to track bank and charge account balances with dedicated keys:

Memory 1 [CHK] [DEP] [BAL] [A]
Memory 2 [PMT] [CHG] [BAL] [B]
Memory 3 [PMT] [CHG] [BAL] [C]
Total sum of Memories [GT]

While the NS103 Data Checker was based on proprietary technology, introduced NEC of Japan with the uPD1833G in 1980 a single-chip calculator circuit that created the blueprint for checkbook-sized Account Manager calculators and thereupon the market got swamped with products based on this design. The uPD1833G simplified the use of the memories by removing the redundant [A], [B], and [C] keys and replaced the inconvenient three-way power-switch of the NS103 Data Checker with two dedicated [ON] and [OFF] keys and a [DS] key to toggle between two entry modes:

Indicator (--) Floating decimal with manual insertion of the decimal using the [.] key
Indicator (AM) Add mode with the decimal automatically put in the dollars and cents position (0.00)

Even the successor of the NS103, known as NS103A, switched its internals to the uPD1833G but we feature some more Account Manager calculators in the Datamath Calculator Museum based on this technology:

Canon Checkbook - Missing the Toggle Key for the decimal mode
Royal LCB 841 - The Art of Perfection in Japan
Royal LCB 835 - Just one Memory (uPD1831G)
Texas Instruments TI-2200 Checkwriter - Late, but not too late
Unisonic LC 262CK Check Master - Credit Card sized

NEC of Japan lost some market share with their design for Account Manager calculators in the Eighties, when competitors like Hitachi and Sharp introduced similar chips and finally lost the business completely to Toshiba's "Solar Cells" compatible design. Find more Account Manager calculators in the Datamath Calculator Museum:

Canon Checkbook II - Toshiba inside
Casio CB-80 - Hitachi inside
Unisonic LC 224CK Check Master - Sharp Inside
Texas Instruments TI-2200 II Checkwriter - Toshiba + Solar cells = Winning formula

Dismantling the featured Datexx DB-403 manufactured in December 2014 in China reveals a clean design centered around an unknown single-chip calculator circuit mounted in Chip-On-Board (COB) technology directly on the printed circuit board and hiding under a small epoxy blob. The electronics is powered by a solar cells and a small LR54 (LR1130) backup battery. Comparing this DB-403 introduced in 2003 with a TI-2200 II Checkwriter from 1987 reveals an almost identical design, main difference is the use of a [Backspace] key to correct entries.

Learn more about single-chip calculator circuits used in Account Manager Calculators.

Don't miss the Corvus CheckMaster introduced by Mostek already in 1975. This rare product retains the balance of your memory even when shut off but uses power-hungry electronics.



If you have additions to the above article please email: joerg@datamath.org.

Joerg Woerner, January 12, 2020. No reprints without written permission.