Longines Symphonette  Electronic Calculator (B Series)

Date of introduction:  1972 Display technology:  LED-modules
New price:   Display size:  8
Size:  5.8" x 3.5" x 1.5"
 147 x 88 x 38 mm3
Weight:  6.7 ounces, 191 grams Serial No:  B 5033
Batteries:  4*NiCd AA Date of manufacture:  mth 12 year 1972
AC-Adapter:  unknown Origin of manufacture:  USA
Precision:  8 Integrated circuits:  TMS0103, 2*SN75491, 2*SN75492
Memories:   Displays:  DIS40, DIS95
Program steps:   Courtesy of:  Joerg Woerner

Just a minor design variation of the original Longines Symphonette Electronic Calculator. Please focus on the color of the numeric keyboard caps of the Klixon™ keyboard.

EC_B_PCB.jpg (290461 Byte)Dismantling the featured Longines Symphonette Electronic Calculator manufactured in December 1972 reveals a typical design based on the TMS0100 single-chip calculator circuit used with the famous Bowmar 901B and powered by four AA-sized rechargeable batteries.

The electronics of the Longines Symphonette Electronic Calculator is centered around a Texas Instruments TMS0103 single-chip calculator circuit and - like most early designs of the wildly successful TMS0100 family - two SN75491 Segment Driver chips and two SN75492 Digit Driver chips, each for the LED display.

The two pre-configured LED-modules (DIS40, DIS95) are based on the TIL360 arrays and soldered directly on the printed circuit board (PCB) of the Electronic Calculator. The remaining components on the PCB are mainly used to generate the necessary supply voltage of the TMS0103 and its clock signal for the internal timing.

Klixon™ is a trademark of Texas Instruments.

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© Joerg Woerner, October 5, 2011. No reprints without written permission.