Privileg 858 MD

Date of introduction:  1976 Display technology:  Fluorescent
New price:   Display size:  8
Size:  5.7" x 2.9" x 0.9"
 146 x 74 x 23 mm3
Weight:  3.9 ounces, 112 grams Serial No:  15972
Batteries:  2*AA Date of manufacture:  mth 01 year 1977
AC-Adapter:   Origin of manufacture:  Japan
Precision:  8 Integrated circuits:  TMS1044 (KSΔ7701)
Memories:  1 Displays:  Futaba 9-ST-10
Program steps:   Courtesy of:  Ken H. Meine
    Download manual: (US: 5.4M Bytes)

Quelle AG was - together with its arch rival Neckermann - one of the leading department stores in Germany and distributed most of their electronic products under the "privileg" label. This Privileg 858 MD calculator caught our attention in 2023 while researching Texas Instruments' TMS1040 Product family of "single-chip calculator circuits" and noticing its interesting keyboard with 31 keys and [∑] sliding switch, a rather unusual combination.

Dismantling this Privileg 858MD manufactured in January 1977 in Japan reveals a very cost effective design using a single-sided printed circuit board (PCB) centered around a TMS1044 single-chip calculator circuit connected to a 9-digit Vacuum Fluorescent Display (VFD), a keyboard assembly and powered by 2 AA-sized alkaline batteries.

The TMS1044 is a member of the TMS1040 Product Family based on the TMS1070 "computer-on-a-chip" introduced in 1974 with the original TMS1000. While the TMS1070 can directly interface with low-voltage VFDs up to 35 Volts does it still need external resistors and a zener diode to bias the anodes and grids of the display with respect to the filament. The TMS1040 added an extra VPP pin to connect a negative 30 Volts bias voltage for its modified output drivers. With the TMS1070 featuring 11 R Outputs for the Digits, 8 O Outputs for the Segments and 4 K Inputs for the Keyboard, reduced the TMS1040 the number of R Outputs to 9, consequently are all known TMS1040 calculator designs using a 9-digit VF Display.

Looking closer onto the PCB you'll notice two diodes placed somehow between the TMS1044 and the keyboard assembly - at first glance an unusual approach. Preparing our DCM-50A Platform to allow the Characterization of Single-Chip Calculator Circuits of the TMS1040 Family, we reverse-engineered the 858 MD calculator and understood that Texas Instruments started to add with the TMS1040 a "virtual" 5th Keyboard Input line by using two additional diodes emulating the 5 K Inputs of the TMC0980 Family. While the TMS0100 single-chip calculator circuit introduced the concept of an 11x4 keyboard matrix scanned with the 11 Digit Outputs and 4 Keyboard Inputs, would the reduction to just 9 Digit Outputs of the TMS1040 allow for only 9x4 keys and switches, in some calculator applications a possible show-stopper. Adding an extra "virtual" Keyboard Input allows consequently for a 9x5 keyboard matrix with up to 45 keys and sliding switches. The TMS1044 was used with a wide range of calculators, the Brinlock Model 806 with 23 keys and Bohsei Model 1000 and with 25 keys marked the lower end, while the Privileg 858MD unleashed the potential of the chip with 31 keys and an additional sliding switch and the Unisonic Model 1040-1 being the middle child with its 27 keys. And yes, we tested the TMS1044 "harvested" from the Bohsei Model 1000 calculator as a Privileg 858MD on the DCM-50A Platform.

Comparing the functionality of these calculators demonstrates the bandwidth of products made possible with the TMS1044 single-chip calculator circuit:

Calculator C
R/CM X<>M X<>Y +/- 1/x x2 x % Δ% PI
Brinlock Model 806   * * *             * *        
Bohsei Model 1000   * *   * *     *   * *   *    
Unisonic Model 1040-1 *   * *     * *      * * *      
Privileg 858MD   * * *   * * * * * * * * * * *

The Canon F-31 using with the TMS1045 another product of the TMS1040 portfolio sports 30 keys and a 4-position switch and hence making good use of the "virtual" 5th Keyboard Input line

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Joerg Woerner, February 10, 2023. No reprints without written permission.