DATAMATH

DATAMATH CALCULATOR MUSEUM

Datexx DB-413

Date of introduction:	December 2002	Display technology:	LCD
New price:	MSRP $25.00 (2002)	Display size:	8+8+4
Size:	3.0" x 6.2" x 0.30" 75 x 157 x 8 mm³
Weight:	3.2 ounces, 91 grams	Serial No:
Batteries:	2*LR43	Date of manufacture:	year 2019
AC-Adapter:		Origin of manufacture:	China
Precision:	8	Integrated circuits:	T66L16
Memories:	3+1+60
Program steps:		Courtesy of:	Joerg Woerner
		Download manual:	(US: 1.2 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-413 manufactured in 2019 in China reveals a clean design centered around a T66L16 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 two small LR43 batteries. Comparing this DB-413 introduced in 2015 with a Canon Checkbook Recorder from 1988 reveals a similar design, main differences are a smaller transaction memory (60 vs. 90 entries) and the missing categories, search function and password.

Don't miss the Radio Shack 65-504 and 65-504A Checkbook Calculators manufactured by Datexx, too.

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.