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Interton PC 2008 (Version 3)

Date of introduction:	August 1973	Display technology:	LED-module
New price:		Display size:	8 + Sign
Size:	5.2" x 3.0" x 1.05" 133 x 76 x 27 mm³
Weight:	5.3 ounces, 149 grams	Serial No:	236317
Batteries:	4*AA	Date of manufacture:	mth 08 year 1973
AC-Adapter:		Origin of manufacture:	Germany
Precision:	8	Integrated circuits:	TMS0128, 2*SN75492
Logic:	Adding Machine	Displays:	9*Monsanto MAN3A
Memories:
Program steps:		Courtesy of:	Joerg Woerner
		Download manual:	(DE: 2.8M Bytes)

Interton Electronic Hörgeräte was founded in 1962 by the brothers Hellmuth Jakob Türk and Hans-Herbert Türk in Cologne as a manufacturer of hearing aids. In January 1973, Interton introduced with the PC 2008 its first electronic calculator before adding in 1975 video game consoles to its portfolio.

When we acquired in 2025 various Interton PC 2008 calculators on our quest to complete the Characterization of Single-Chip Calculator Circuits of General Instrument's C-500 Product Family of Single-chip Calculator Circuits, we noticed some differences with their keyboards. Both the PC 2008 (Version 1) with its rare TMR 012 brain and the PC 2008 (Version 2) with the more common C-550 chip have a dedicate [K] key while this PC 2008 (Version 3) is using a switch to select Constant Mode.

Dismantling the featured Interton PC 2008 (Version 3) calculator manufactured in August 1973 in Germany reveals a rather complex design based on two double-sided printed circuit boards (PCBs) for its electronics and keyboard, a display module, a DC/DC converter module and powered by four AA-sized batteries or an external power adapter.

The Main-PCB is centered around a Texas Instruments TMS0128 single-chip calculator circuit and two SN75492 drivers for the LED display module with its nine Monsanto MAN3A Seven-Segment. A single-sided DC/DC converter module is soldered piggy-back on the Main-PCB, it is providing not only the negative supply voltage of the TMS0128, but providing its clock signal, too.

The TMS0128 used with the Interton PC 2008 (Version 3) is a member of the second generation of Texas Instruments' TMS0100 Product Family and traces back to the famous TMS1802 introduced already in September 1971:

• 1971: GEN1 TMS0100: ROM (320 Words * 11 Bits), SAM (13 Digits Registers), external display drivers
• 1973: GEN2 TMS0600: Increased ROM (384 Words * 11 Bits), Identical SAM (13 Digits Registers), external display drivers. Process shrink, higher functionality
• 1973: GEN2 TMS0700: Identical ROM (320 Words * 11 Bits), Identical SAM (13 Digits Registers), external display drivers. Process shrink, identical functionality, cost reduction of IC
• 1973: GEN2 TMS0800: Identical ROM (320 Words * 11 Bits), Reduced SAM (11 Digits Registers), integrated segment drivers. Process shrink, reduced functionality, higher integration

Comparing the feature sets of the General Instrument C-550/TMR012 single-chip calculator circuits with the TMS0128 makes you wonder why Interton made such a radical change from the first two versions of the PC 2008 calculator without changing its product name:

Type	Calculators	Keyboard	Constant (M-D-A-S)	Digits	Fixed DP	Rounding	Special Functions
TMR 012	PC 2008 (Version 1)	[+][−][=]	2-2-2-2	8	Float 10^-20-10⁷⁹	None	Constant Number Constant Function
C-550	PC 2008 (Version 2)	[+][−][=]	2-2-2-2	8	Float 10^-20-10⁷⁹	None	Constant Number Constant Function
TMS0128	PC 2008 (Version 3)	[+=][−=]	1-2-X-X	8 + Sign	0-7, F	5/4	[^A/_D][%][‰][00]

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